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 $184.50   9.482%   $201.9943   $201.99   $202.00   $202.00  
  Purchase #2 $39.49   10.557%   $43.659   $43.66   $43.65   $43.70  
  Purchase #3 $165.58   7.781%   $178.4638   $178.46   $178.45   $178.50  
  Purchase #4 $157.43   5.333%   $165.8257   $165.83   $165.85   $165.80  
  Purchase #5 $34.78   12.450%   $39.1101   $39.11   $39.10   $39.10  
  Purchase #6 $180.78   5.261%   $190.2908   $190.29   $190.30   $190.30  
  Purchase #7 $184.78   5.144%   $194.2851   $194.29   $194.30   $194.30  
  7 purchase totals = $947.34       $1,013.6288   $1,013.63   $1,013.65   $1,013.70