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 $70.37   6.571%   $74.994   $74.99   $75.00   $75.00  
  Purchase #2 $238.67   11.859%   $266.9739   $266.97   $266.95   $267.00  
  Purchase #3 $236.96   6.452%   $252.2487   $252.25   $252.25   $252.20  
  Purchase #4 $128.65   4.374%   $134.2772   $134.28   $134.30   $134.30  
  Purchase #5 $133.52   5.298%   $140.5939   $140.59   $140.60   $140.60  
  Purchase #6 $148.40   4.629%   $155.2694   $155.27   $155.25   $155.30  
  Purchase #7 $21.59   6.644%   $23.0244   $23.02   $23.00   $23.00  
  7 purchase totals = $978.16       $1,047.3815   $1,047.37   $1,047.35   $1,047.40