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 $86.96   8.118%   $94.0194   $94.02   $94.00   $94.00  
  Purchase #2 $128.32   5.716%   $135.6548   $135.65   $135.65   $135.70  
  Purchase #3 $153.49   9.535%   $168.1253   $168.13   $168.15   $168.10  
  Purchase #4 $124.47   3.349%   $128.6385   $128.64   $128.65   $128.60  
  Purchase #5 $171.64   11.606%   $191.5605   $191.56   $191.55   $191.60  
  Purchase #6 $197.79   11.167%   $219.8772   $219.88   $219.90   $219.90  
  Purchase #7 $52.85   8.102%   $57.1319   $57.13   $57.15   $57.10  
  7 purchase totals = $915.52       $995.0076   $995.01   $995.05   $995.00