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	$213.76	13.723%	$243.0943	$243.09	$243.10	$243.10
Purchase #2	$205.39	11.750%	$229.5233	$229.52	$229.50	$229.50
Purchase #3	$125.63	7.150%	$134.6125	$134.61	$134.60	$134.60
Purchase #4	$45.41	11.629%	$50.6907	$50.69	$50.70	$50.70
Purchase #5	$123.84	10.861%	$137.2903	$137.29	$137.30	$137.30
Purchase #6	$61.35	4.364%	$64.0273	$64.03	$64.05	$64.00
Purchase #7	$100.72	8.543%	$109.3245	$109.32	$109.30	$109.30
7 purchase totals =	$876.10		$968.5629	$968.55	$968.55	$968.50