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	$122.28	4.210%	$127.428	$127.43	$127.45	$127.40
Purchase #2	$10.65	4.388%	$11.1173	$11.12	$11.10	$11.10
Purchase #3	$33.46	13.751%	$38.0611	$38.06	$38.05	$38.10
Purchase #4	$138.28	10.115%	$152.267	$152.27	$152.25	$152.30
Purchase #5	$90.69	4.594%	$94.8563	$94.86	$94.85	$94.90
Purchase #6	$233.65	9.718%	$256.3561	$256.36	$256.35	$256.40
Purchase #7	$60.47	7.738%	$65.1492	$65.15	$65.15	$65.10
7 purchase totals =	$689.48		$745.2350	$745.25	$745.20	$745.30