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 $48.28   11.717%   $53.937   $53.94   $53.95   $53.90  
  Purchase #2 $109.83   5.353%   $115.7092   $115.71   $115.70   $115.70  
  Purchase #3 $217.93   11.522%   $243.0399   $243.04   $243.05   $243.00  
  Purchase #4 $231.78   5.450%   $244.412   $244.41   $244.40   $244.40  
  Purchase #5 $145.76   10.590%   $161.196   $161.20   $161.20   $161.20  
  Purchase #6 $189.97   10.839%   $210.5608   $210.56   $210.55   $210.60  
  Purchase #7 $62.49   5.554%   $65.9607   $65.96   $65.95   $66.00  
  7 purchase totals = $1,006.04       $1,094.8156   $1,094.82   $1,094.80   $1,094.80