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	$95.59	4.151%	$99.5579	$99.56	$99.55	$99.60
Purchase #2	$180.64	4.488%	$188.7471	$188.75	$188.75	$188.70
Purchase #3	$189.65	10.868%	$210.2612	$210.26	$210.25	$210.30
Purchase #4	$241.47	8.261%	$261.4178	$261.42	$261.40	$261.40
Purchase #5	$103.25	8.420%	$111.9437	$111.94	$111.95	$111.90
Purchase #6	$37.41	5.234%	$39.368	$39.37	$39.35	$39.40
Purchase #7	$134.25	11.842%	$150.1479	$150.15	$150.15	$150.10
7 purchase totals =	$982.26		$1,061.4436	$1,061.45	$1,061.40	$1,061.40