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	$245.32	12.212%	$275.2785	$275.28	$275.30	$275.30
Purchase #2	$155.40	11.602%	$173.4295	$173.43	$173.45	$173.40
Purchase #3	$77.99	5.520%	$82.295	$82.30	$82.30	$82.30
Purchase #4	$47.30	12.621%	$53.2697	$53.27	$53.25	$53.30
Purchase #5	$165.64	8.263%	$179.3268	$179.33	$179.35	$179.30
Purchase #6	$243.80	8.242%	$263.894	$263.89	$263.90	$263.90
Purchase #7	$83.32	10.811%	$92.3277	$92.33	$92.35	$92.30
7 purchase totals =	$1,018.77		$1,119.8212	$1,119.83	$1,119.90	$1,119.80