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 $56.56   5.663%   $59.763   $59.76   $59.75   $59.80  
  Purchase #2 $200.52   7.760%   $216.0804   $216.08   $216.10   $216.10  
  Purchase #3 $150.65   7.476%   $161.9126   $161.91   $161.90   $161.90  
  Purchase #4 $210.87   10.289%   $232.5664   $232.57   $232.55   $232.60  
  Purchase #5 $22.64   4.721%   $23.7088   $23.71   $23.70   $23.70  
  Purchase #6 $158.30   13.643%   $179.8969   $179.90   $179.90   $179.90  
  Purchase #7 $130.38   11.245%   $145.0412   $145.04   $145.05   $145.00  
  7 purchase totals = $929.92       $1,018.9693   $1,018.97   $1,018.95   $1,019.00