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	$60.77	5.565%	$64.1519	$64.15	$64.15	$64.20
Purchase #2	$77.36	13.679%	$87.9421	$87.94	$87.95	$87.90
Purchase #3	$189.82	3.614%	$196.6801	$196.68	$196.70	$196.70
Purchase #4	$182.91	4.684%	$191.4775	$191.48	$191.50	$191.50
Purchase #5	$193.68	10.824%	$214.6439	$214.64	$214.65	$214.60
Purchase #6	$175.71	7.380%	$188.6774	$188.68	$188.70	$188.70
Purchase #7	$72.36	8.435%	$78.4636	$78.46	$78.45	$78.50
7 purchase totals =	$952.61		$1,022.0365	$1,022.03	$1,022.10	$1,022.10