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 $54.59   13.489%   $61.9536   $61.95   $61.95   $62.00  
  Purchase #2 $96.91   10.247%   $106.8404   $106.84   $106.85   $106.80  
  Purchase #3 $197.49   13.581%   $224.3111   $224.31   $224.30   $224.30  
  Purchase #4 $109.98   9.727%   $120.6778   $120.68   $120.70   $120.70  
  Purchase #5 $187.48   3.530%   $194.098   $194.10   $194.10   $194.10  
  Purchase #6 $232.54   13.582%   $264.1236   $264.12   $264.10   $264.10  
  Purchase #7 $144.44   12.827%   $162.9673   $162.97   $162.95   $163.00  
  7 purchase totals = $1,023.43       $1,134.9718   $1,134.97   $1,134.95   $1,135.00