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	$143.53	11.210%	$159.6197	$159.62	$159.60	$159.60
Purchase #2	$130.31	13.857%	$148.3671	$148.37	$148.35	$148.40
Purchase #3	$90.40	10.784%	$100.1487	$100.15	$100.15	$100.10
Purchase #4	$99.46	11.346%	$110.7447	$110.74	$110.75	$110.70
Purchase #5	$134.38	13.222%	$152.1477	$152.15	$152.15	$152.10
Purchase #6	$142.95	12.134%	$160.2956	$160.30	$160.30	$160.30
Purchase #7	$38.68	6.283%	$41.1103	$41.11	$41.10	$41.10
7 purchase totals =	$779.71		$872.4338	$872.44	$872.40	$872.30