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 $83.80   13.459%   $95.0786   $95.08   $95.10   $95.10  
  Purchase #2 $157.33   6.285%   $167.2182   $167.22   $167.20   $167.20  
  Purchase #3 $59.25   8.415%   $64.2359   $64.24   $64.25   $64.20  
  Purchase #4 $200.82   9.788%   $220.4763   $220.48   $220.50   $220.50  
  Purchase #5 $124.64   11.258%   $138.672   $138.67   $138.65   $138.70  
  Purchase #6 $76.96   5.252%   $81.0019   $81.00   $81.00   $81.00  
  Purchase #7 $26.86   5.459%   $28.3263   $28.33   $28.35   $28.30  
  7 purchase totals = $729.66       $795.0092   $795.02   $795.05   $795.00