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 $174.51   12.684%   $196.6448   $196.64   $196.65   $196.60  
  Purchase #2 $183.79   6.383%   $195.5213   $195.52   $195.50   $195.50  
  Purchase #3 $161.46   8.457%   $175.1147   $175.11   $175.10   $175.10  
  Purchase #4 $126.35   5.298%   $133.044   $133.04   $133.05   $133.00  
  Purchase #5 $104.81   8.425%   $113.6402   $113.64   $113.65   $113.60  
  Purchase #6 $33.53   11.635%   $37.4312   $37.43   $37.45   $37.40  
  Purchase #7 $192.49   6.480%   $204.9634   $204.96   $204.95   $205.00  
  7 purchase totals = $976.94       $1,056.3596   $1,056.34   $1,056.35   $1,056.20