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 $14.68   11.442%   $16.3597   $16.36   $16.35   $16.40  
  Purchase #2 $91.27   6.656%   $97.3449   $97.34   $97.35   $97.30  
  Purchase #3 $175.26   10.330%   $193.3644   $193.36   $193.35   $193.40  
  Purchase #4 $189.52   12.873%   $213.9169   $213.92   $213.90   $213.90  
  Purchase #5 $231.34   6.261%   $245.8242   $245.82   $245.80   $245.80  
  Purchase #6 $100.37   3.230%   $103.612   $103.61   $103.60   $103.60  
  Purchase #7 $211.83   5.707%   $223.9191   $223.92   $223.90   $223.90  
  7 purchase totals = $1,014.27       $1,094.3412   $1,094.33   $1,094.25   $1,094.30