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 $214.32   7.633%   $230.679   $230.68   $230.70   $230.70  
  Purchase #2 $213.78   11.485%   $238.3326   $238.33   $238.35   $238.30  
  Purchase #3 $109.85   12.564%   $123.6516   $123.65   $123.65   $123.70  
  Purchase #4 $231.34   10.604%   $255.8713   $255.87   $255.85   $255.90  
  Purchase #5 $202.94   3.195%   $209.4239   $209.42   $209.40   $209.40  
  Purchase #6 $218.46   13.173%   $247.2377   $247.24   $247.25   $247.20  
  Purchase #7 $56.28   10.307%   $62.0808   $62.08   $62.10   $62.10  
  7 purchase totals = $1,246.97       $1,367.2769   $1,367.27   $1,367.30   $1,367.30