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	$159.81	7.736%	$172.1729	$172.17	$172.15	$172.20
Purchase #2	$96.63	12.431%	$108.6421	$108.64	$108.65	$108.60
Purchase #3	$155.79	7.168%	$166.957	$166.96	$166.95	$167.00
Purchase #4	$81.77	10.569%	$90.4123	$90.41	$90.40	$90.40
Purchase #5	$40.44	12.506%	$45.4974	$45.50	$45.50	$45.50
Purchase #6	$92.71	11.276%	$103.164	$103.16	$103.15	$103.20
Purchase #7	$164.56	10.255%	$181.4356	$181.44	$181.45	$181.40
7 purchase totals =	$791.71		$868.2813	$868.28	$868.25	$868.30