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 $59.67   5.474%   $62.9363   $62.94   $62.95   $62.90  
  Purchase #2 $12.77   13.433%   $14.4854   $14.49   $14.50   $14.50  
  Purchase #3 $53.33   6.435%   $56.7618   $56.76   $56.75   $56.80  
  Purchase #4 $167.82   9.219%   $183.2913   $183.29   $183.30   $183.30  
  Purchase #5 $217.43   5.837%   $230.1214   $230.12   $230.10   $230.10  
  Purchase #6 $135.93   6.789%   $145.1583   $145.16   $145.15   $145.20  
  Purchase #7 $231.91   10.716%   $256.7615   $256.76   $256.75   $256.80  
  7 purchase totals = $878.86       $949.5160   $949.52   $949.50   $949.60