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 $58.75   4.334%   $61.2962   $61.30   $61.30   $61.30  
  Purchase #2 $184.37   13.705%   $209.6379   $209.64   $209.65   $209.60  
  Purchase #3 $93.44   4.733%   $97.8625   $97.86   $97.85   $97.90  
  Purchase #4 $204.72   11.682%   $228.6354   $228.64   $228.65   $228.60  
  Purchase #5 $245.77   4.296%   $256.3283   $256.33   $256.35   $256.30  
  Purchase #6 $96.50   10.673%   $106.7994   $106.80   $106.80   $106.80  
  Purchase #7 $194.35   5.339%   $204.7263   $204.73   $204.75   $204.70  
  7 purchase totals = $1,077.90       $1,165.2860   $1,165.30   $1,165.35   $1,165.20