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	$248.62	13.303%	$281.6939	$281.69	$281.70	$281.70
Purchase #2	$28.89	10.590%	$31.9495	$31.95	$31.95	$31.90
Purchase #3	$6.35	4.553%	$6.6391	$6.64	$6.65	$6.60
Purchase #4	$92.44	8.310%	$100.1218	$100.12	$100.10	$100.10
Purchase #5	$172.40	10.692%	$190.833	$190.83	$190.85	$190.80
Purchase #6	$147.78	12.127%	$165.7013	$165.70	$165.70	$165.70
Purchase #7	$231.88	4.297%	$241.8439	$241.84	$241.85	$241.80
7 purchase totals =	$928.36		$1,018.7825	$1,018.77	$1,018.80	$1,018.60