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	$137.60	10.487%	$152.0301	$152.03	$152.05	$152.00
Purchase #2	$24.27	3.529%	$25.1265	$25.13	$25.15	$25.10
Purchase #3	$114.91	11.680%	$128.3315	$128.33	$128.35	$128.30
Purchase #4	$70.45	13.160%	$79.7212	$79.72	$79.70	$79.70
Purchase #5	$66.56	6.847%	$71.1174	$71.12	$71.10	$71.10
Purchase #6	$164.82	7.810%	$177.6924	$177.69	$177.70	$177.70
Purchase #7	$120.71	5.454%	$127.2935	$127.29	$127.30	$127.30
7 purchase totals =	$699.32		$761.3126	$761.31	$761.35	$761.20