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	$49.80	8.449%	$54.0076	$54.01	$54.00	$54.00
Purchase #2	$75.71	12.481%	$85.1594	$85.16	$85.15	$85.20
Purchase #3	$250.68	6.473%	$266.9065	$266.91	$266.90	$266.90
Purchase #4	$166.54	4.574%	$174.1575	$174.16	$174.15	$174.20
Purchase #5	$11.54	5.570%	$12.1828	$12.18	$12.20	$12.20
Purchase #6	$26.64	11.346%	$29.6626	$29.66	$29.65	$29.70
Purchase #7	$90.34	9.827%	$99.2177	$99.22	$99.20	$99.20
7 purchase totals =	$671.25		$721.2941	$721.30	$721.25	$721.40