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 $88.55   10.724%   $98.0461   $98.05   $98.05   $98.00  
  Purchase #2 $246.99   8.227%   $267.3099   $267.31   $267.30   $267.30  
  Purchase #3 $202.93   13.400%   $230.1226   $230.12   $230.10   $230.10  
  Purchase #4 $222.88   5.412%   $234.9423   $234.94   $234.95   $234.90  
  Purchase #5 $177.82   7.240%   $190.6942   $190.69   $190.70   $190.70  
  Purchase #6 $153.36   9.114%   $167.3372   $167.34   $167.35   $167.30  
  Purchase #7 $27.98   4.127%   $29.1347   $29.13   $29.15   $29.10  
  7 purchase totals = $1,120.51       $1,217.5870   $1,217.58   $1,217.60   $1,217.40