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	$196.82	10.580%	$217.6436	$217.64	$217.65	$217.60
Purchase #2	$86.48	3.542%	$89.5431	$89.54	$89.55	$89.50
Purchase #3	$172.92	10.817%	$191.6248	$191.62	$191.60	$191.60
Purchase #4	$138.61	6.684%	$147.8747	$147.87	$147.85	$147.90
Purchase #5	$225.96	4.227%	$235.5113	$235.51	$235.50	$235.50
Purchase #6	$167.60	13.630%	$190.4439	$190.44	$190.45	$190.40
Purchase #7	$78.31	8.543%	$85	$85.00	$85.00	$85.00
7 purchase totals =	$1,066.70		$1,157.6414	$1,157.62	$1,157.60	$1,157.50