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 $60.93   3.331%   $62.9596   $62.96   $62.95   $63.00  
  Purchase #2 $221.71   5.454%   $233.8021   $233.80   $233.80   $233.80  
  Purchase #3 $11.57   7.132%   $12.3952   $12.40   $12.40   $12.40  
  Purchase #4 $35.96   4.704%   $37.6516   $37.65   $37.65   $37.70  
  Purchase #5 $140.57   3.679%   $145.7416   $145.74   $145.75   $145.70  
  Purchase #6 $161.65   6.723%   $172.5177   $172.52   $172.50   $172.50  
  Purchase #7 $195.91   4.272%   $204.2793   $204.28   $204.30   $204.30  
  7 purchase totals = $828.30       $869.3471   $869.35   $869.35   $869.40