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 $46.26   12.691%   $52.1309   $52.13   $52.15   $52.10  
  Purchase #2 $196.93   4.374%   $205.5437   $205.54   $205.55   $205.50  
  Purchase #3 $9.90   4.414%   $10.337   $10.34   $10.35   $10.30  
  Purchase #4 $204.72   10.139%   $225.4766   $225.48   $225.50   $225.50  
  Purchase #5 $126.52   5.463%   $133.4318   $133.43   $133.45   $133.40  
  Purchase #6 $214.89   6.302%   $228.4324   $228.43   $228.45   $228.40  
  Purchase #7 $174.68   8.238%   $189.0701   $189.07   $189.05   $189.10  
  7 purchase totals = $973.90       $1,044.4225   $1,044.42   $1,044.50   $1,044.30