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	$57.85	6.601%	$61.6687	$61.67	$61.65	$61.70
Purchase #2	$136.52	7.372%	$146.5843	$146.58	$146.60	$146.60
Purchase #3	$84.32	12.198%	$94.6054	$94.61	$94.60	$94.60
Purchase #4	$202.35	10.624%	$223.8477	$223.85	$223.85	$223.80
Purchase #5	$150.27	5.637%	$158.7407	$158.74	$158.75	$158.70
Purchase #6	$119.80	3.513%	$124.0086	$124.01	$124.00	$124.00
Purchase #7	$227.82	13.298%	$258.1155	$258.12	$258.10	$258.10
7 purchase totals =	$978.93		$1,067.5709	$1,067.58	$1,067.55	$1,067.50