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	$160.96	8.819%	$175.1551	$175.16	$175.15	$175.20
Purchase #2	$149.33	4.354%	$155.8318	$155.83	$155.85	$155.80
Purchase #3	$100.46	8.261%	$108.759	$108.76	$108.75	$108.80
Purchase #4	$105.52	5.294%	$111.1062	$111.11	$111.10	$111.10
Purchase #5	$131.25	5.503%	$138.4727	$138.47	$138.45	$138.50
Purchase #6	$141.54	4.817%	$148.358	$148.36	$148.35	$148.40
Purchase #7	$186.55	10.748%	$206.6004	$206.60	$206.60	$206.60
7 purchase totals =	$975.61		$1,044.2832	$1,044.29	$1,044.25	$1,044.40