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 $40.95   9.792%   $44.9598   $44.96   $44.95   $45.00  
  Purchase #2 $193.75   4.737%   $202.9279   $202.93   $202.95   $202.90  
  Purchase #3 $120.97   5.319%   $127.4044   $127.40   $127.40   $127.40  
  Purchase #4 $167.46   9.645%   $183.6115   $183.61   $183.60   $183.60  
  Purchase #5 $38.43   6.597%   $40.9652   $40.97   $40.95   $41.00  
  Purchase #6 $209.82   12.261%   $235.546   $235.55   $235.55   $235.50  
  Purchase #7 $204.52   13.743%   $232.6272   $232.63   $232.65   $232.60  
  7 purchase totals = $975.90       $1,068.0420   $1,068.05   $1,068.05   $1,068.00