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	$51.68	4.343%	$53.9245	$53.92	$53.90	$53.90
Purchase #2	$139.55	8.589%	$151.5359	$151.54	$151.55	$151.50
Purchase #3	$155.33	6.323%	$165.1515	$165.15	$165.15	$165.20
Purchase #4	$159.32	3.761%	$165.312	$165.31	$165.30	$165.30
Purchase #5	$43.80	13.351%	$49.6477	$49.65	$49.65	$49.60
Purchase #6	$226.96	9.261%	$247.9788	$247.98	$248.00	$248.00
Purchase #7	$156.53	9.487%	$171.38	$171.38	$171.40	$171.40
7 purchase totals =	$933.17		$1,004.9304	$1,004.93	$1,004.95	$1,004.90