Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $108.65   5.561%   $114.692   $114.69   $114.70   $114.70  
  Purchase #2 $216.48   12.412%   $243.3495   $243.35   $243.35   $243.30  
  Purchase #3 $167.77   6.773%   $179.1331   $179.13   $179.15   $179.10  
  Purchase #4 $194.66   4.779%   $203.9628   $203.96   $203.95   $204.00  
  Purchase #5 $169.78   11.185%   $188.7699   $188.77   $188.75   $188.80  
  Purchase #6 $192.79   5.230%   $202.8729   $202.87   $202.85   $202.90  
  Purchase #7 $126.34   12.759%   $142.4597   $142.46   $142.45   $142.50  
  7 purchase totals = $1,176.47       $1,275.2399   $1,275.23   $1,275.20   $1,275.30