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	$69.39	4.120%	$72.2489	$72.25	$72.25	$72.20
Purchase #2	$22.63	8.698%	$24.5984	$24.60	$24.60	$24.60
Purchase #3	$117.30	11.857%	$131.2083	$131.21	$131.20	$131.20
Purchase #4	$118.94	7.113%	$127.4002	$127.40	$127.40	$127.40
Purchase #5	$178.67	5.301%	$188.1413	$188.14	$188.15	$188.10
Purchase #6	$105.92	10.768%	$117.3255	$117.33	$117.35	$117.30
Purchase #7	$145.94	13.134%	$165.1078	$165.11	$165.10	$165.10
7 purchase totals =	$758.79		$826.0304	$826.04	$826.05	$825.90