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 $214.99   4.649%   $224.9849   $224.98   $225.00   $225.00  
  Purchase #2 $157.68   12.582%   $177.5193   $177.52   $177.50   $177.50  
  Purchase #3 $241.70   12.771%   $272.5675   $272.57   $272.55   $272.60  
  Purchase #4 $38.28   13.304%   $43.3728   $43.37   $43.35   $43.40  
  Purchase #5 $209.65   13.785%   $238.5503   $238.55   $238.55   $238.60  
  Purchase #6 $60.88   6.531%   $64.8561   $64.86   $64.85   $64.90  
  Purchase #7 $45.55   10.175%   $50.1847   $50.18   $50.20   $50.20  
  7 purchase totals = $968.73       $1,072.0356   $1,072.03   $1,072.00   $1,072.20