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	$159.96	3.222%	$165.1139	$165.11	$165.10	$165.10
Purchase #2	$59.91	4.592%	$62.6611	$62.66	$62.65	$62.70
Purchase #3	$96.84	6.721%	$103.3486	$103.35	$103.35	$103.30
Purchase #4	$24.67	5.372%	$25.9953	$26.00	$26.00	$26.00
Purchase #5	$168.72	3.308%	$174.3013	$174.30	$174.30	$174.30
Purchase #6	$17.77	4.211%	$18.5183	$18.52	$18.50	$18.50
Purchase #7	$95.39	4.323%	$99.5137	$99.51	$99.50	$99.50
7 purchase totals =	$623.26		$649.4522	$649.45	$649.40	$649.40