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	$44.61	6.663%	$47.5824	$47.58	$47.60	$47.60
Purchase #2	$58.66	3.160%	$60.5137	$60.51	$60.50	$60.50
Purchase #3	$139.42	7.865%	$150.3854	$150.39	$150.40	$150.40
Purchase #4	$91.98	5.722%	$97.2431	$97.24	$97.25	$97.20
Purchase #5	$23.81	4.697%	$24.9284	$24.93	$24.95	$24.90
Purchase #6	$103.61	7.428%	$111.3062	$111.31	$111.30	$111.30
Purchase #7	$64.79	11.358%	$72.1488	$72.15	$72.15	$72.10
7 purchase totals =	$526.88		$564.1080	$564.11	$564.15	$564.00