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	$238.66	12.803%	$269.2156	$269.22	$269.20	$269.20
Purchase #2	$179.95	11.114%	$199.9496	$199.95	$199.95	$199.90
Purchase #3	$186.81	5.520%	$197.1219	$197.12	$197.10	$197.10
Purchase #4	$133.57	11.451%	$148.8651	$148.87	$148.85	$148.90
Purchase #5	$93.78	12.454%	$105.4594	$105.46	$105.45	$105.50
Purchase #6	$11.73	4.239%	$12.2272	$12.23	$12.25	$12.20
Purchase #7	$137.83	3.362%	$142.4638	$142.46	$142.45	$142.50
7 purchase totals =	$982.33		$1,075.3026	$1,075.31	$1,075.25	$1,075.30