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	$223.66	3.326%	$231.0989	$231.10	$231.10	$231.10
Purchase #2	$60.73	11.370%	$67.635	$67.64	$67.65	$67.60
Purchase #3	$82.96	5.207%	$87.2797	$87.28	$87.30	$87.30
Purchase #4	$114.91	13.537%	$130.4654	$130.47	$130.45	$130.50
Purchase #5	$185.80	10.812%	$205.8887	$205.89	$205.90	$205.90
Purchase #6	$235.70	12.603%	$265.4053	$265.41	$265.40	$265.40
Purchase #7	$48.84	13.664%	$55.5135	$55.51	$55.50	$55.50
7 purchase totals =	$952.60		$1,043.2865	$1,043.30	$1,043.30	$1,043.30