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 $85.98   9.416%   $94.0759   $94.08   $94.10   $94.10  
  Purchase #2 $212.81   11.525%   $237.3364   $237.34   $237.35   $237.30  
  Purchase #3 $161.53   11.476%   $180.0672   $180.07   $180.05   $180.10  
  Purchase #4 $203.56   3.267%   $210.2103   $210.21   $210.20   $210.20  
  Purchase #5 $212.93   3.260%   $219.8715   $219.87   $219.85   $219.90  
  Purchase #6 $102.87   5.819%   $108.856   $108.86   $108.85   $108.90  
  Purchase #7 $231.45   5.169%   $243.4137   $243.41   $243.40   $243.40  
  7 purchase totals = $1,211.13       $1,293.8310   $1,293.84   $1,293.80   $1,293.90