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 $126.59   4.285%   $132.0144   $132.01   $132.00   $132.00  
  Purchase #2 $244.47   5.658%   $258.3021   $258.30   $258.30   $258.30  
  Purchase #3 $112.67   6.284%   $119.7502   $119.75   $119.75   $119.80  
  Purchase #4 $241.50   5.318%   $254.343   $254.34   $254.35   $254.30  
  Purchase #5 $101.53   3.535%   $105.1191   $105.12   $105.10   $105.10  
  Purchase #6 $117.87   5.767%   $124.6676   $124.67   $124.65   $124.70  
  Purchase #7 $22.52   12.807%   $25.4041   $25.40   $25.40   $25.40  
  7 purchase totals = $967.15       $1,019.6005   $1,019.59   $1,019.55   $1,019.60