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 $232.54   4.627%   $243.2996   $243.30   $243.30   $243.30  
  Purchase #2 $43.88   9.169%   $47.9034   $47.90   $47.90   $47.90  
  Purchase #3 $188.37   4.715%   $197.2516   $197.25   $197.25   $197.30  
  Purchase #4 $213.37   8.152%   $230.7639   $230.76   $230.75   $230.80  
  Purchase #5 $22.85   7.503%   $24.5644   $24.56   $24.55   $24.60  
  Purchase #6 $152.50   4.231%   $158.9523   $158.95   $158.95   $159.00  
  Purchase #7 $176.77   9.213%   $193.0558   $193.06   $193.05   $193.10  
  7 purchase totals = $1,030.28       $1,095.7910   $1,095.78   $1,095.75   $1,096.00