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	$158.81	8.593%	$172.4565	$172.46	$172.45	$172.50
Purchase #2	$222.54	7.274%	$238.7276	$238.73	$238.75	$238.70
Purchase #3	$65.56	11.680%	$73.2174	$73.22	$73.20	$73.20
Purchase #4	$62.57	12.168%	$70.1835	$70.18	$70.20	$70.20
Purchase #5	$225.54	8.484%	$244.6748	$244.67	$244.65	$244.70
Purchase #6	$101.96	6.230%	$108.3121	$108.31	$108.30	$108.30
Purchase #7	$53.35	11.740%	$59.6133	$59.61	$59.60	$59.60
7 purchase totals =	$890.33		$967.1852	$967.18	$967.15	$967.20