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	$75.91	10.518%	$83.8942	$83.89	$83.90	$83.90
Purchase #2	$71.83	8.475%	$77.9176	$77.92	$77.90	$77.90
Purchase #3	$45.88	4.329%	$47.8661	$47.87	$47.85	$47.90
Purchase #4	$101.85	7.541%	$109.5305	$109.53	$109.55	$109.50
Purchase #5	$136.34	4.504%	$142.4808	$142.48	$142.50	$142.50
Purchase #6	$111.28	5.667%	$117.5862	$117.59	$117.60	$117.60
Purchase #7	$141.99	4.196%	$147.9479	$147.95	$147.95	$147.90
7 purchase totals =	$685.08		$727.2233	$727.23	$727.25	$727.20