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 $44.76   4.230%   $46.6533   $46.65   $46.65   $46.70  
  Purchase #2 $196.49   10.194%   $216.5202   $216.52   $216.50   $216.50  
  Purchase #3 $24.79   11.528%   $27.6478   $27.65   $27.65   $27.60  
  Purchase #4 $225.67   4.332%   $235.446   $235.45   $235.45   $235.40  
  Purchase #5 $242.27   10.553%   $267.8368   $267.84   $267.85   $267.80  
  Purchase #6 $141.66   13.495%   $160.777   $160.78   $160.80   $160.80  
  Purchase #7 $190.65   13.352%   $216.1056   $216.11   $216.10   $216.10  
  7 purchase totals = $1,066.29       $1,170.9867   $1,171.00   $1,171.00   $1,170.90