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	$222.27	9.624%	$243.6613	$243.66	$243.65	$243.70
Purchase #2	$84.26	6.431%	$89.6788	$89.68	$89.70	$89.70
Purchase #3	$213.75	12.832%	$241.1784	$241.18	$241.20	$241.20
Purchase #4	$193.89	11.313%	$215.8248	$215.82	$215.80	$215.80
Purchase #5	$56.69	5.337%	$59.7155	$59.72	$59.70	$59.70
Purchase #6	$238.72	9.121%	$260.4937	$260.49	$260.50	$260.50
Purchase #7	$34.55	4.670%	$36.1635	$36.16	$36.15	$36.20
7 purchase totals =	$1,044.13		$1,146.7160	$1,146.71	$1,146.70	$1,146.80