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	$76.52	12.734%	$86.2641	$86.26	$86.25	$86.30
Purchase #2	$157.69	4.808%	$165.2717	$165.27	$165.25	$165.30
Purchase #3	$28.77	13.621%	$32.6888	$32.69	$32.70	$32.70
Purchase #4	$88.31	3.150%	$91.0918	$91.09	$91.10	$91.10
Purchase #5	$200.41	13.419%	$227.303	$227.30	$227.30	$227.30
Purchase #6	$73.88	6.472%	$78.6615	$78.66	$78.65	$78.70
Purchase #7	$203.89	10.198%	$224.6827	$224.68	$224.70	$224.70
7 purchase totals =	$829.47		$905.9636	$905.95	$905.95	$906.10