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	$218.51	3.225%	$225.5569	$225.56	$225.55	$225.60
Purchase #2	$106.80	6.590%	$113.8381	$113.84	$113.85	$113.80
Purchase #3	$60.30	4.389%	$62.9466	$62.95	$62.95	$62.90
Purchase #4	$85.89	9.306%	$93.8829	$93.88	$93.90	$93.90
Purchase #5	$216.73	3.619%	$224.5735	$224.57	$224.55	$224.60
Purchase #6	$200.66	12.256%	$225.2529	$225.25	$225.25	$225.30
Purchase #7	$226.88	10.556%	$250.8295	$250.83	$250.85	$250.80
7 purchase totals =	$1,115.77		$1,196.8804	$1,196.88	$1,196.90	$1,196.90