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 $85.48   9.394%   $93.51   $93.51   $93.50   $93.50  
  Purchase #2 $219.44   12.829%   $247.592   $247.59   $247.60   $247.60  
  Purchase #3 $229.30   11.873%   $256.5248   $256.52   $256.50   $256.50  
  Purchase #4 $212.87   3.713%   $220.7739   $220.77   $220.75   $220.80  
  Purchase #5 $50.29   5.719%   $53.1661   $53.17   $53.15   $53.20  
  Purchase #6 $78.28   13.276%   $88.6725   $88.67   $88.65   $88.70  
  Purchase #7 $138.63   11.461%   $154.5184   $154.52   $154.50   $154.50  
  7 purchase totals = $1,014.29       $1,114.7577   $1,114.75   $1,114.65   $1,114.80