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	$180.73	7.219%	$193.7769	$193.78	$193.80	$193.80
Purchase #2	$70.25	5.852%	$74.361	$74.36	$74.35	$74.40
Purchase #3	$127.49	10.625%	$141.0358	$141.04	$141.05	$141.00
Purchase #4	$131.69	7.391%	$141.4232	$141.42	$141.40	$141.40
Purchase #5	$73.52	11.371%	$81.88	$81.88	$81.90	$81.90
Purchase #6	$51.83	3.261%	$53.5202	$53.52	$53.50	$53.50
Purchase #7	$56.83	4.314%	$59.2816	$59.28	$59.30	$59.30
7 purchase totals =	$692.34		$745.2787	$745.28	$745.30	$745.30