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 $197.35   8.851%   $214.8174   $214.82   $214.80   $214.80  
  Purchase #2 $204.37   5.568%   $215.7493   $215.75   $215.75   $215.70  
  Purchase #3 $116.25   11.118%   $129.1747   $129.17   $129.15   $129.20  
  Purchase #4 $112.72   8.246%   $122.0149   $122.01   $122.00   $122.00  
  Purchase #5 $191.27   5.450%   $201.6942   $201.69   $201.70   $201.70  
  Purchase #6 $110.29   12.423%   $123.9913   $123.99   $124.00   $124.00  
  Purchase #7 $14.50   11.540%   $16.1733   $16.17   $16.15   $16.20  
  7 purchase totals = $946.75       $1,023.6151   $1,023.60   $1,023.55   $1,023.60