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	$99.64	5.242%	$104.8631	$104.86	$104.85	$104.90
Purchase #2	$11.61	5.280%	$12.223	$12.22	$12.20	$12.20
Purchase #3	$123.98	4.428%	$129.4698	$129.47	$129.45	$129.50
Purchase #4	$29.96	8.272%	$32.4383	$32.44	$32.45	$32.40
Purchase #5	$89.29	4.757%	$93.5375	$93.54	$93.55	$93.50
Purchase #6	$30.37	10.845%	$33.6636	$33.66	$33.65	$33.70
Purchase #7	$112.78	4.768%	$118.1574	$118.16	$118.15	$118.20
7 purchase totals =	$497.63		$524.3527	$524.35	$524.30	$524.40