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 $83.27   10.435%   $91.9592   $91.96   $91.95   $92.00  
  Purchase #2 $223.91   9.462%   $245.0964   $245.10   $245.10   $245.10  
  Purchase #3 $156.30   10.237%   $172.3004   $172.30   $172.30   $172.30  
  Purchase #4 $174.34   11.443%   $194.2897   $194.29   $194.30   $194.30  
  Purchase #5 $60.27   9.672%   $66.0993   $66.10   $66.10   $66.10  
  Purchase #6 $117.33   3.104%   $120.9719   $120.97   $120.95   $121.00  
  Purchase #7 $186.73   9.647%   $204.7438   $204.74   $204.75   $204.70  
  7 purchase totals = $1,002.15       $1,095.4607   $1,095.46   $1,095.45   $1,095.50