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 $141.46   7.688%   $152.3354   $152.34   $152.35   $152.30  
  Purchase #2 $174.98   13.346%   $198.3328   $198.33   $198.35   $198.30  
  Purchase #3 $125.90   7.639%   $135.5175   $135.52   $135.50   $135.50  
  Purchase #4 $36.56   5.566%   $38.5949   $38.59   $38.60   $38.60  
  Purchase #5 $144.33   11.629%   $161.1141   $161.11   $161.10   $161.10  
  Purchase #6 $43.73   4.733%   $45.7997   $45.80   $45.80   $45.80  
  Purchase #7 $22.98   7.496%   $24.7026   $24.70   $24.70   $24.70  
  7 purchase totals = $689.94       $756.3970   $756.39   $756.40   $756.30