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	$247.26	3.283%	$255.3775	$255.38	$255.40	$255.40
Purchase #2	$40.48	5.425%	$42.676	$42.68	$42.70	$42.70
Purchase #3	$146.36	8.842%	$159.3012	$159.30	$159.30	$159.30
Purchase #4	$200.90	8.717%	$218.4125	$218.41	$218.40	$218.40
Purchase #5	$157.33	10.199%	$173.3761	$173.38	$173.40	$173.40
Purchase #6	$58.49	10.375%	$64.5583	$64.56	$64.55	$64.60
Purchase #7	$231.45	4.336%	$241.4857	$241.49	$241.50	$241.50
7 purchase totals =	$1,082.27		$1,155.1873	$1,155.20	$1,155.25	$1,155.30