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 $60.95   13.553%   $69.2106   $69.21   $69.20   $69.20  
  Purchase #2 $181.68   10.614%   $200.9635   $200.96   $200.95   $201.00  
  Purchase #3 $219.82   10.845%   $243.6595   $243.66   $243.65   $243.70  
  Purchase #4 $80.65   9.523%   $88.3303   $88.33   $88.35   $88.30  
  Purchase #5 $239.72   11.334%   $266.8899   $266.89   $266.90   $266.90  
  Purchase #6 $203.97   9.346%   $223.033   $223.03   $223.05   $223.00  
  Purchase #7 $190.90   4.588%   $199.6585   $199.66   $199.65   $199.70  
  7 purchase totals = $1,177.69       $1,291.7453   $1,291.74   $1,291.75   $1,291.80