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	$17.74	10.380%	$19.5814	$19.58	$19.60	$19.60
Purchase #2	$103.32	7.332%	$110.8954	$110.90	$110.90	$110.90
Purchase #3	$157.72	6.379%	$167.781	$167.78	$167.80	$167.80
Purchase #4	$187.57	4.379%	$195.7837	$195.78	$195.80	$195.80
Purchase #5	$74.52	10.222%	$82.1374	$82.14	$82.15	$82.10
Purchase #6	$118.86	3.496%	$123.0153	$123.02	$123.00	$123.00
Purchase #7	$135.74	13.143%	$153.5803	$153.58	$153.60	$153.60
7 purchase totals =	$795.47		$852.7745	$852.78	$852.85	$852.80