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	$84.32	12.241%	$94.6416	$94.64	$94.65	$94.60
Purchase #2	$40.80	6.175%	$43.3194	$43.32	$43.30	$43.30
Purchase #3	$200.87	10.407%	$221.7745	$221.77	$221.75	$221.80
Purchase #4	$230.69	11.116%	$256.3335	$256.33	$256.35	$256.30
Purchase #5	$178.28	4.586%	$186.4559	$186.46	$186.45	$186.50
Purchase #6	$229.57	11.733%	$256.5054	$256.51	$256.50	$256.50
Purchase #7	$99.83	7.647%	$107.464	$107.46	$107.45	$107.50
7 purchase totals =	$1,064.36		$1,166.4943	$1,166.49	$1,166.45	$1,166.50