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	$215.25	6.195%	$228.5847	$228.58	$228.60	$228.60
Purchase #2	$33.68	8.666%	$36.5987	$36.60	$36.60	$36.60
Purchase #3	$140.79	4.269%	$146.8003	$146.80	$146.80	$146.80
Purchase #4	$147.45	3.196%	$152.1625	$152.16	$152.15	$152.20
Purchase #5	$146.63	6.676%	$156.419	$156.42	$156.40	$156.40
Purchase #6	$55.89	11.811%	$62.4912	$62.49	$62.50	$62.50
Purchase #7	$126.66	3.321%	$130.8664	$130.87	$130.85	$130.90
7 purchase totals =	$866.35		$913.9228	$913.92	$913.90	$914.00