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 $61.86   3.220%   $63.8519   $63.85   $63.85   $63.90  
  Purchase #2 $229.25   13.620%   $260.4739   $260.47   $260.45   $260.50  
  Purchase #3 $229.49   12.668%   $258.5618   $258.56   $258.55   $258.60  
  Purchase #4 $247.60   11.710%   $276.594   $276.59   $276.60   $276.60  
  Purchase #5 $81.76   11.348%   $91.0381   $91.04   $91.05   $91.00  
  Purchase #6 $118.52   9.125%   $129.335   $129.34   $129.35   $129.30  
  Purchase #7 $150.25   9.854%   $165.0556   $165.06   $165.05   $165.10  
  7 purchase totals = $1,118.73       $1,244.9103   $1,244.91   $1,244.90   $1,245.00