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 $60.85   3.426%   $62.9347   $62.93   $62.95   $62.90  
  Purchase #2 $205.92   13.145%   $232.9882   $232.99   $233.00   $233.00  
  Purchase #3 $173.70   10.455%   $191.8603   $191.86   $191.85   $191.90  
  Purchase #4 $237.88   8.158%   $257.2863   $257.29   $257.30   $257.30  
  Purchase #5 $93.85   6.194%   $99.6631   $99.66   $99.65   $99.70  
  Purchase #6 $219.97   12.455%   $247.3673   $247.37   $247.35   $247.40  
  Purchase #7 $243.43   8.675%   $264.5476   $264.55   $264.55   $264.50  
  7 purchase totals = $1,235.60       $1,356.6475   $1,356.65   $1,356.65   $1,356.70