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 $57.70   7.529%   $62.0442   $62.04   $62.05   $62.00  
  Purchase #2 $192.44   6.696%   $205.3258   $205.33   $205.35   $205.30  
  Purchase #3 $15.74   7.778%   $16.9643   $16.96   $16.95   $17.00  
  Purchase #4 $54.40   8.582%   $59.0686   $59.07   $59.05   $59.10  
  Purchase #5 $231.96   5.199%   $244.0196   $244.02   $244.00   $244.00  
  Purchase #6 $167.27   6.524%   $178.1827   $178.18   $178.20   $178.20  
  Purchase #7 $77.95   12.844%   $87.9619   $87.96   $87.95   $88.00  
  7 purchase totals = $797.46       $853.5671   $853.56   $853.55   $853.60