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	$30.73	4.494%	$32.111	$32.11	$32.10	$32.10
Purchase #2	$43.38	4.505%	$45.3343	$45.33	$45.35	$45.30
Purchase #3	$137.45	5.136%	$144.5094	$144.51	$144.50	$144.50
Purchase #4	$202.44	5.485%	$213.5438	$213.54	$213.55	$213.50
Purchase #5	$235.42	8.413%	$255.2259	$255.23	$255.25	$255.20
Purchase #6	$129.68	7.149%	$138.9508	$138.95	$138.95	$139.00
Purchase #7	$165.36	9.829%	$181.6132	$181.61	$181.60	$181.60
7 purchase totals =	$944.46		$1,011.2884	$1,011.28	$1,011.30	$1,011.20