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 $191.33   9.834%   $210.1454   $210.15   $210.15   $210.10  
  Purchase #2 $24.95   5.536%   $26.3312   $26.33   $26.35   $26.30  
  Purchase #3 $204.82   6.720%   $218.5839   $218.58   $218.60   $218.60  
  Purchase #4 $174.67   11.287%   $194.385   $194.39   $194.40   $194.40  
  Purchase #5 $147.54   3.133%   $152.1624   $152.16   $152.15   $152.20  
  Purchase #6 $165.30   9.282%   $180.6431   $180.64   $180.65   $180.60  
  Purchase #7 $26.46   6.852%   $28.273   $28.27   $28.25   $28.30  
  7 purchase totals = $935.07       $1,010.5240   $1,010.52   $1,010.55   $1,010.50