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 $14.28   5.261%   $15.0313   $15.03   $15.05   $15.00  
  Purchase #2 $91.65   5.765%   $96.9336   $96.93   $96.95   $96.90  
  Purchase #3 $222.96   10.805%   $247.0508   $247.05   $247.05   $247.10  
  Purchase #4 $209.79   5.302%   $220.9131   $220.91   $220.90   $220.90  
  Purchase #5 $109.98   13.591%   $124.9274   $124.93   $124.95   $124.90  
  Purchase #6 $157.76   6.111%   $167.4007   $167.40   $167.40   $167.40  
  Purchase #7 $206.72   4.505%   $216.0327   $216.03   $216.05   $216.00  
  7 purchase totals = $1,013.14       $1,088.2896   $1,088.28   $1,088.35   $1,088.20