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 $147.93   3.115%   $152.538   $152.54   $152.55   $152.50  
  Purchase #2 $214.77   12.555%   $241.7344   $241.73   $241.75   $241.70  
  Purchase #3 $214.90   3.821%   $223.1113   $223.11   $223.10   $223.10  
  Purchase #4 $233.58   5.855%   $247.2561   $247.26   $247.25   $247.30  
  Purchase #5 $175.79   10.636%   $194.487   $194.49   $194.50   $194.50  
  Purchase #6 $226.52   9.205%   $247.3712   $247.37   $247.35   $247.40  
  Purchase #7 $53.84   9.409%   $58.9058   $58.91   $58.90   $58.90  
  7 purchase totals = $1,267.33       $1,365.4038   $1,365.41   $1,365.40   $1,365.40