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 $59.58   4.636%   $62.3421   $62.34   $62.35   $62.30  
  Purchase #2 $212.65   10.128%   $234.1872   $234.19   $234.20   $234.20  
  Purchase #3 $207.34   3.777%   $215.1712   $215.17   $215.15   $215.20  
  Purchase #4 $47.41   4.398%   $49.4951   $49.50   $49.50   $49.50  
  Purchase #5 $231.60   6.582%   $246.8439   $246.84   $246.85   $246.80  
  Purchase #6 $219.62   12.415%   $246.8858   $246.89   $246.90   $246.90  
  Purchase #7 $38.66   11.800%   $43.2219   $43.22   $43.20   $43.20  
  7 purchase totals = $1,016.86       $1,098.1472   $1,098.15   $1,098.15   $1,098.10