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	$127.96	10.290%	$141.1271	$141.13	$141.15	$141.10
Purchase #2	$9.82	10.823%	$10.8828	$10.88	$10.90	$10.90
Purchase #3	$154.48	7.801%	$166.531	$166.53	$166.55	$166.50
Purchase #4	$234.53	8.862%	$255.314	$255.31	$255.30	$255.30
Purchase #5	$172.84	13.347%	$195.909	$195.91	$195.90	$195.90
Purchase #6	$152.28	5.297%	$160.3463	$160.35	$160.35	$160.30
Purchase #7	$36.37	13.540%	$41.2945	$41.29	$41.30	$41.30
7 purchase totals =	$888.28		$971.4047	$971.40	$971.45	$971.30