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	$243.33	10.757%	$269.505	$269.51	$269.50	$269.50
Purchase #2	$85.54	10.174%	$94.2428	$94.24	$94.25	$94.20
Purchase #3	$121.55	7.281%	$130.4001	$130.40	$130.40	$130.40
Purchase #4	$172.97	11.727%	$193.2542	$193.25	$193.25	$193.30
Purchase #5	$114.64	10.424%	$126.5901	$126.59	$126.60	$126.60
Purchase #6	$69.49	13.433%	$78.8246	$78.82	$78.80	$78.80
Purchase #7	$108.39	3.637%	$112.3321	$112.33	$112.35	$112.30
7 purchase totals =	$915.91		$1,005.1489	$1,005.14	$1,005.15	$1,005.10