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 $33.49   6.754%   $35.7519   $35.75   $35.75   $35.80  
  Purchase #2 $126.45   4.728%   $132.4286   $132.43   $132.45   $132.40  
  Purchase #3 $223.35   8.306%   $241.9015   $241.90   $241.90   $241.90  
  Purchase #4 $174.38   13.684%   $198.2422   $198.24   $198.25   $198.20  
  Purchase #5 $41.52   12.796%   $46.8329   $46.83   $46.85   $46.80  
  Purchase #6 $191.95   5.241%   $202.0101   $202.01   $202.00   $202.00  
  Purchase #7 $228.96   8.165%   $247.6546   $247.65   $247.65   $247.70  
  7 purchase totals = $1,020.10       $1,104.8218   $1,104.81   $1,104.85   $1,104.80