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 $67.52   10.565%   $74.6535   $74.65   $74.65   $74.70  
  Purchase #2 $209.59   13.455%   $237.7903   $237.79   $237.80   $237.80  
  Purchase #3 $184.73   8.216%   $199.9074   $199.91   $199.90   $199.90  
  Purchase #4 $34.34   9.276%   $37.5254   $37.53   $37.55   $37.50  
  Purchase #5 $50.96   13.756%   $57.9701   $57.97   $57.95   $58.00  
  Purchase #6 $200.83   8.476%   $217.8524   $217.85   $217.85   $217.90  
  Purchase #7 $186.51   7.680%   $200.834   $200.83   $200.85   $200.80  
  7 purchase totals = $934.48       $1,026.5331   $1,026.53   $1,026.55   $1,026.60