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 $5.64   7.430%   $6.0591   $6.06   $6.05   $6.10  
  Purchase #2 $227.25   6.229%   $241.4054   $241.41   $241.40   $241.40  
  Purchase #3 $23.35   6.351%   $24.833   $24.83   $24.85   $24.80  
  Purchase #4 $121.79   9.171%   $132.9594   $132.96   $132.95   $133.00  
  Purchase #5 $97.67   10.432%   $107.8589   $107.86   $107.85   $107.90  
  Purchase #6 $38.73   6.615%   $41.292   $41.29   $41.30   $41.30  
  Purchase #7 $189.96   8.554%   $206.2092   $206.21   $206.20   $206.20  
  7 purchase totals = $704.39       $760.6170   $760.62   $760.60   $760.70