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 $188.49   13.822%   $214.5431   $214.54   $214.55   $214.50  
  Purchase #2 $173.91   11.362%   $193.6697   $193.67   $193.65   $193.70  
  Purchase #3 $229.57   11.121%   $255.1005   $255.10   $255.10   $255.10  
  Purchase #4 $40.63   8.130%   $43.9332   $43.93   $43.95   $43.90  
  Purchase #5 $156.86   6.700%   $167.3696   $167.37   $167.35   $167.40  
  Purchase #6 $166.77   4.287%   $173.9194   $173.92   $173.90   $173.90  
  Purchase #7 $106.85   13.511%   $121.2865   $121.29   $121.30   $121.30  
  7 purchase totals = $1,063.08       $1,169.8220   $1,169.82   $1,169.80   $1,169.80