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	$153.67	12.213%	$172.4377	$172.44	$172.45	$172.40
Purchase #2	$160.54	7.247%	$172.1743	$172.17	$172.15	$172.20
Purchase #3	$75.98	9.663%	$83.3219	$83.32	$83.30	$83.30
Purchase #4	$250.38	7.805%	$269.9222	$269.92	$269.90	$269.90
Purchase #5	$169.91	8.540%	$184.4203	$184.42	$184.40	$184.40
Purchase #6	$115.73	12.830%	$130.5782	$130.58	$130.60	$130.60
Purchase #7	$106.55	7.753%	$114.8108	$114.81	$114.80	$114.80
7 purchase totals =	$1,032.76		$1,127.6654	$1,127.66	$1,127.60	$1,127.60