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	$96.70	7.479%	$103.9322	$103.93	$103.95	$103.90
Purchase #2	$109.86	12.173%	$123.2333	$123.23	$123.25	$123.20
Purchase #3	$149.59	6.774%	$159.7232	$159.72	$159.70	$159.70
Purchase #4	$165.77	13.180%	$187.6185	$187.62	$187.60	$187.60
Purchase #5	$114.97	7.445%	$123.5295	$123.53	$123.55	$123.50
Purchase #6	$145.61	3.840%	$151.2014	$151.20	$151.20	$151.20
Purchase #7	$219.79	12.595%	$247.4726	$247.47	$247.45	$247.50
7 purchase totals =	$1,002.29		$1,096.7107	$1,096.70	$1,096.70	$1,096.60