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	$231.98	13.166%	$262.5225	$262.52	$262.50	$262.50
Purchase #2	$76.92	6.735%	$82.1006	$82.10	$82.10	$82.10
Purchase #3	$130.94	10.158%	$144.2409	$144.24	$144.25	$144.20
Purchase #4	$17.86	8.205%	$19.3254	$19.33	$19.35	$19.30
Purchase #5	$92.89	7.465%	$99.8242	$99.82	$99.80	$99.80
Purchase #6	$216.73	8.748%	$235.6895	$235.69	$235.70	$235.70
Purchase #7	$126.76	4.705%	$132.7241	$132.72	$132.70	$132.70
7 purchase totals =	$894.08		$976.4272	$976.42	$976.40	$976.30