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 $71.52   3.446%   $73.9846   $73.98   $74.00   $74.00  
  Purchase #2 $223.52   10.161%   $246.2319   $246.23   $246.25   $246.20  
  Purchase #3 $156.73   5.778%   $165.7859   $165.79   $165.80   $165.80  
  Purchase #4 $206.51   3.144%   $213.0027   $213.00   $213.00   $213.00  
  Purchase #5 $145.54   9.447%   $159.2892   $159.29   $159.30   $159.30  
  Purchase #6 $62.63   3.747%   $64.9767   $64.98   $65.00   $65.00  
  Purchase #7 $7.90   12.800%   $8.9112   $8.91   $8.90   $8.90  
  7 purchase totals = $874.35       $932.1822   $932.18   $932.25   $932.20