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	$133.73	7.501%	$143.7611	$143.76	$143.75	$143.80
Purchase #2	$55.88	10.136%	$61.544	$61.54	$61.55	$61.50
Purchase #3	$83.84	12.485%	$94.3074	$94.31	$94.30	$94.30
Purchase #4	$152.85	9.408%	$167.2301	$167.23	$167.25	$167.20
Purchase #5	$44.72	12.624%	$50.3655	$50.37	$50.35	$50.40
Purchase #6	$137.95	6.766%	$147.2837	$147.28	$147.30	$147.30
Purchase #7	$68.64	5.625%	$72.501	$72.50	$72.50	$72.50
7 purchase totals =	$677.61		$736.9928	$736.99	$737.00	$737.00