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	$161.66	6.642%	$172.3975	$172.40	$172.40	$172.40
Purchase #2	$221.65	10.415%	$244.7348	$244.73	$244.75	$244.70
Purchase #3	$50.68	7.655%	$54.5596	$54.56	$54.55	$54.60
Purchase #4	$150.39	10.411%	$166.0471	$166.05	$166.05	$166.00
Purchase #5	$141.66	9.627%	$155.2976	$155.30	$155.30	$155.30
Purchase #6	$223.71	13.652%	$254.2509	$254.25	$254.25	$254.30
Purchase #7	$57.89	11.208%	$64.3783	$64.38	$64.40	$64.40
7 purchase totals =	$1,007.64		$1,111.6658	$1,111.67	$1,111.70	$1,111.70