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	$229.53	13.106%	$259.6122	$259.61	$259.60	$259.60
Purchase #2	$187.33	6.479%	$199.4671	$199.47	$199.45	$199.50
Purchase #3	$200.92	7.345%	$215.6776	$215.68	$215.70	$215.70
Purchase #4	$42.51	13.517%	$48.2561	$48.26	$48.25	$48.30
Purchase #5	$68.66	5.224%	$72.2468	$72.25	$72.25	$72.20
Purchase #6	$159.27	8.200%	$172.3301	$172.33	$172.35	$172.30
Purchase #7	$152.61	7.574%	$164.1687	$164.17	$164.15	$164.20
7 purchase totals =	$1,040.83		$1,131.7586	$1,131.77	$1,131.75	$1,131.80