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 $204.60   7.124%   $219.1757   $219.18   $219.20   $219.20  
  Purchase #2 $244.88   4.180%   $255.116   $255.12   $255.10   $255.10  
  Purchase #3 $88.91   5.859%   $94.1192   $94.12   $94.10   $94.10  
  Purchase #4 $139.90   3.293%   $144.5069   $144.51   $144.50   $144.50  
  Purchase #5 $236.89   11.471%   $264.0637   $264.06   $264.05   $264.10  
  Purchase #6 $205.52   5.780%   $217.3991   $217.40   $217.40   $217.40  
  Purchase #7 $7.36   5.179%   $7.7412   $7.74   $7.75   $7.70  
  7 purchase totals = $1,128.06       $1,202.1218   $1,202.13   $1,202.10   $1,202.10