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 $211.78   9.866%   $232.6742   $232.67   $232.65   $232.70  
  Purchase #2 $163.37   9.629%   $179.1009   $179.10   $179.10   $179.10  
  Purchase #3 $112.50   3.363%   $116.2834   $116.28   $116.30   $116.30  
  Purchase #4 $95.86   7.845%   $103.3802   $103.38   $103.40   $103.40  
  Purchase #5 $202.81   10.569%   $224.245   $224.25   $224.25   $224.20  
  Purchase #6 $67.39   9.833%   $74.0165   $74.02   $74.00   $74.00  
  Purchase #7 $74.48   8.254%   $80.6276   $80.63   $80.65   $80.60  
  7 purchase totals = $928.19       $1,010.3278   $1,010.33   $1,010.35   $1,010.30