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	$136.88	12.269%	$153.6738	$153.67	$153.65	$153.70
Purchase #2	$238.60	13.419%	$270.6177	$270.62	$270.60	$270.60
Purchase #3	$109.57	4.211%	$114.184	$114.18	$114.20	$114.20
Purchase #4	$223.47	13.434%	$253.491	$253.49	$253.50	$253.50
Purchase #5	$49.65	9.714%	$54.473	$54.47	$54.45	$54.50
Purchase #6	$144.58	9.791%	$158.7358	$158.74	$158.75	$158.70
Purchase #7	$100.97	4.586%	$105.6005	$105.60	$105.60	$105.60
7 purchase totals =	$1,003.72		$1,110.7758	$1,110.77	$1,110.75	$1,110.80