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	$52.63	4.194%	$54.8373	$54.84	$54.85	$54.80
Purchase #2	$25.72	4.117%	$26.7789	$26.78	$26.80	$26.80
Purchase #3	$85.42	10.300%	$94.2183	$94.22	$94.20	$94.20
Purchase #4	$84.97	4.344%	$88.6611	$88.66	$88.65	$88.70
Purchase #5	$168.58	10.174%	$185.7313	$185.73	$185.75	$185.70
Purchase #6	$41.97	3.630%	$43.4935	$43.49	$43.50	$43.50
Purchase #7	$9.32	13.577%	$10.5854	$10.59	$10.60	$10.60
7 purchase totals =	$468.61		$504.3058	$504.31	$504.35	$504.30