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 $43.53   5.865%   $46.083   $46.08   $46.10   $46.10  
  Purchase #2 $247.82   5.839%   $262.2902   $262.29   $262.30   $262.30  
  Purchase #3 $147.30   5.236%   $155.0126   $155.01   $155.00   $155.00  
  Purchase #4 $65.42   12.760%   $73.7676   $73.77   $73.75   $73.80  
  Purchase #5 $23.88   6.702%   $25.4804   $25.48   $25.50   $25.50  
  Purchase #6 $11.85   9.663%   $12.9951   $13.00   $13.00   $13.00  
  Purchase #7 $130.28   4.771%   $136.4957   $136.50   $136.50   $136.50  
  7 purchase totals = $670.08       $712.1246   $712.13   $712.15   $712.20