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 $70.85   5.771%   $74.9388   $74.94   $74.95   $74.90  
  Purchase #2 $123.40   5.769%   $130.5189   $130.52   $130.50   $130.50  
  Purchase #3 $47.84   6.822%   $51.1036   $51.10   $51.10   $51.10  
  Purchase #4 $231.96   5.594%   $244.9358   $244.94   $244.95   $244.90  
  Purchase #5 $57.69   5.703%   $60.9801   $60.98   $61.00   $61.00  
  Purchase #6 $203.92   5.121%   $214.3627   $214.36   $214.35   $214.40  
  Purchase #7 $234.32   5.630%   $247.5122   $247.51   $247.50   $247.50  
  7 purchase totals = $969.98       $1,024.3521   $1,024.35   $1,024.35   $1,024.30