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	$46.69	11.534%	$52.0752	$52.08	$52.10	$52.10
Purchase #2	$120.30	9.614%	$131.8656	$131.87	$131.85	$131.90
Purchase #3	$38.57	8.173%	$41.7223	$41.72	$41.70	$41.70
Purchase #4	$108.79	10.753%	$120.4882	$120.49	$120.50	$120.50
Purchase #5	$81.75	13.388%	$92.6947	$92.69	$92.70	$92.70
Purchase #6	$149.72	6.594%	$159.5925	$159.59	$159.60	$159.60
Purchase #7	$175.37	11.856%	$196.1619	$196.16	$196.15	$196.20
7 purchase totals =	$721.19		$794.6004	$794.60	$794.60	$794.70