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	$172.54	7.567%	$185.5961	$185.60	$185.60	$185.60
Purchase #2	$144.80	13.651%	$164.5666	$164.57	$164.55	$164.60
Purchase #3	$188.65	7.117%	$202.0762	$202.08	$202.10	$202.10
Purchase #4	$171.57	11.766%	$191.7569	$191.76	$191.75	$191.80
Purchase #5	$73.52	7.346%	$78.9208	$78.92	$78.90	$78.90
Purchase #6	$175.38	9.127%	$191.3869	$191.39	$191.40	$191.40
Purchase #7	$15.37	10.757%	$17.0234	$17.02	$17.00	$17.00
7 purchase totals =	$941.83		$1,031.3269	$1,031.34	$1,031.30	$1,031.40