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 $218.96   5.463%   $230.9218   $230.92   $230.90   $230.90  
  Purchase #2 $64.48   6.283%   $68.5313   $68.53   $68.55   $68.50  
  Purchase #3 $88.85   6.742%   $94.8403   $94.84   $94.85   $94.80  
  Purchase #4 $41.57   6.557%   $44.2957   $44.30   $44.30   $44.30  
  Purchase #5 $102.76   10.805%   $113.8632   $113.86   $113.85   $113.90  
  Purchase #6 $142.56   7.782%   $153.654   $153.65   $153.65   $153.70  
  Purchase #7 $187.89   3.722%   $194.8833   $194.88   $194.90   $194.90  
  7 purchase totals = $847.07       $900.9896   $900.98   $901.00   $901.00