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 $62.41   9.699%   $68.4631   $68.46   $68.45   $68.50  
  Purchase #2 $20.88   5.473%   $22.0228   $22.02   $22.00   $22.00  
  Purchase #3 $217.85   10.222%   $240.1186   $240.12   $240.10   $240.10  
  Purchase #4 $150.79   13.767%   $171.5493   $171.55   $171.55   $171.50  
  Purchase #5 $219.31   6.845%   $234.3218   $234.32   $234.30   $234.30  
  Purchase #6 $197.71   12.221%   $221.8721   $221.87   $221.85   $221.90  
  Purchase #7 $59.90   6.471%   $63.7761   $63.78   $63.80   $63.80  
  7 purchase totals = $928.85       $1,022.1238   $1,022.12   $1,022.05   $1,022.10