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	$111.44	10.305%	$122.9239	$122.92	$122.90	$122.90
Purchase #2	$182.71	11.733%	$204.1474	$204.15	$204.15	$204.10
Purchase #3	$78.57	4.658%	$82.2298	$82.23	$82.25	$82.20
Purchase #4	$167.89	11.226%	$186.7373	$186.74	$186.75	$186.70
Purchase #5	$31.97	10.798%	$35.4221	$35.42	$35.40	$35.40
Purchase #6	$100.27	5.185%	$105.469	$105.47	$105.45	$105.50
Purchase #7	$148.27	10.714%	$164.1556	$164.16	$164.15	$164.20
7 purchase totals =	$821.12		$901.0851	$901.09	$901.05	$901.00