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	$246.38	7.472%	$264.7895	$264.79	$264.80	$264.80
Purchase #2	$73.45	7.312%	$78.8207	$78.82	$78.80	$78.80
Purchase #3	$246.74	11.710%	$275.6333	$275.63	$275.65	$275.60
Purchase #4	$108.45	3.157%	$111.8738	$111.87	$111.85	$111.90
Purchase #5	$18.99	8.494%	$20.603	$20.60	$20.60	$20.60
Purchase #6	$169.98	13.380%	$192.7233	$192.72	$192.70	$192.70
Purchase #7	$197.63	4.127%	$205.7862	$205.79	$205.80	$205.80
7 purchase totals =	$1,061.62		$1,150.2298	$1,150.22	$1,150.20	$1,150.20