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	$153.30	13.580%	$174.1181	$174.12	$174.10	$174.10
Purchase #2	$57.83	5.345%	$60.921	$60.92	$60.90	$60.90
Purchase #3	$59.61	13.869%	$67.8773	$67.88	$67.90	$67.90
Purchase #4	$223.68	10.709%	$247.6339	$247.63	$247.65	$247.60
Purchase #5	$205.29	12.184%	$230.3025	$230.30	$230.30	$230.30
Purchase #6	$30.53	13.362%	$34.6094	$34.61	$34.60	$34.60
Purchase #7	$170.49	9.580%	$186.8229	$186.82	$186.80	$186.80
7 purchase totals =	$900.73		$1,002.2851	$1,002.28	$1,002.25	$1,002.20