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 $94.66   6.809%   $101.1054   $101.11   $101.10   $101.10  
  Purchase #2 $169.32   13.184%   $191.6431   $191.64   $191.65   $191.60  
  Purchase #3 $83.70   10.400%   $92.4048   $92.40   $92.40   $92.40  
  Purchase #4 $204.49   8.390%   $221.6467   $221.65   $221.65   $221.60  
  Purchase #5 $171.70   11.820%   $191.9949   $191.99   $192.00   $192.00  
  Purchase #6 $197.57   8.737%   $214.8317   $214.83   $214.85   $214.80  
  Purchase #7 $136.96   4.173%   $142.6753   $142.68   $142.70   $142.70  
  7 purchase totals = $1,058.40       $1,156.3019   $1,156.30   $1,156.35   $1,156.20