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 $27.59   5.842%   $29.2018   $29.20   $29.20   $29.20  
  Purchase #2 $203.42   9.274%   $222.2852   $222.29   $222.30   $222.30  
  Purchase #3 $113.88   11.388%   $126.8487   $126.85   $126.85   $126.80  
  Purchase #4 $160.63   8.262%   $173.9013   $173.90   $173.90   $173.90  
  Purchase #5 $179.95   9.668%   $197.3476   $197.35   $197.35   $197.30  
  Purchase #6 $120.77   7.529%   $129.8628   $129.86   $129.85   $129.90  
  Purchase #7 $212.96   10.155%   $234.5861   $234.59   $234.60   $234.60  
  7 purchase totals = $1,019.20       $1,114.0335   $1,114.04   $1,114.05   $1,114.00