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	$234.47	12.726%	$264.3087	$264.31	$264.30	$264.30
Purchase #2	$65.27	12.727%	$73.5769	$73.58	$73.60	$73.60
Purchase #3	$58.89	11.332%	$65.5634	$65.56	$65.55	$65.60
Purchase #4	$123.97	10.820%	$137.3836	$137.38	$137.40	$137.40
Purchase #5	$156.90	8.634%	$170.4467	$170.45	$170.45	$170.40
Purchase #6	$181.38	3.172%	$187.1334	$187.13	$187.15	$187.10
Purchase #7	$83.89	12.550%	$94.4182	$94.42	$94.40	$94.40
7 purchase totals =	$904.77		$992.8309	$992.83	$992.85	$992.80