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 $223.44   9.546%   $244.7696   $244.77   $244.75   $244.80  
  Purchase #2 $112.35   11.417%   $125.177   $125.18   $125.20   $125.20  
  Purchase #3 $118.79   11.634%   $132.61   $132.61   $132.60   $132.60  
  Purchase #4 $100.25   6.644%   $106.9106   $106.91   $106.90   $106.90  
  Purchase #5 $144.31   11.442%   $160.822   $160.82   $160.80   $160.80  
  Purchase #6 $216.79   6.612%   $231.1242   $231.12   $231.10   $231.10  
  Purchase #7 $87.25   7.437%   $93.7388   $93.74   $93.75   $93.70  
  7 purchase totals = $1,003.18       $1,095.1522   $1,095.15   $1,095.10   $1,095.10