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	$216.76	10.234%	$238.9432	$238.94	$238.95	$238.90
Purchase #2	$122.83	3.305%	$126.8895	$126.89	$126.90	$126.90
Purchase #3	$170.40	8.326%	$184.5875	$184.59	$184.60	$184.60
Purchase #4	$224.83	13.426%	$255.0157	$255.02	$255.00	$255.00
Purchase #5	$184.61	13.361%	$209.2757	$209.28	$209.30	$209.30
Purchase #6	$231.54	5.607%	$244.5224	$244.52	$244.50	$244.50
Purchase #7	$170.28	4.735%	$178.3428	$178.34	$178.35	$178.30
7 purchase totals =	$1,321.25		$1,437.5768	$1,437.58	$1,437.60	$1,437.50