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	$85.45	12.609%	$96.2244	$96.22	$96.20	$96.20
Purchase #2	$57.41	7.476%	$61.702	$61.70	$61.70	$61.70
Purchase #3	$30.75	11.213%	$34.198	$34.20	$34.20	$34.20
Purchase #4	$229.72	3.731%	$238.2909	$238.29	$238.30	$238.30
Purchase #5	$200.52	5.587%	$211.7231	$211.72	$211.70	$211.70
Purchase #6	$91.25	9.669%	$100.073	$100.07	$100.05	$100.10
Purchase #7	$179.32	6.129%	$190.3105	$190.31	$190.30	$190.30
7 purchase totals =	$874.42		$932.5219	$932.51	$932.45	$932.50