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	$147.56	12.255%	$165.6435	$165.64	$165.65	$165.60
Purchase #2	$96.89	13.354%	$109.8287	$109.83	$109.85	$109.80
Purchase #3	$137.37	11.252%	$152.8269	$152.83	$152.85	$152.80
Purchase #4	$143.68	11.838%	$160.6888	$160.69	$160.70	$160.70
Purchase #5	$214.40	6.808%	$228.9964	$229.00	$229.00	$229.00
Purchase #6	$32.89	13.267%	$37.2535	$37.25	$37.25	$37.30
Purchase #7	$240.93	7.168%	$258.1999	$258.20	$258.20	$258.20
7 purchase totals =	$1,013.72		$1,113.4377	$1,113.44	$1,113.50	$1,113.40