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	$234.36	8.340%	$253.9056	$253.91	$253.90	$253.90
Purchase #2	$136.29	4.380%	$142.2595	$142.26	$142.25	$142.30
Purchase #3	$22.58	4.739%	$23.6501	$23.65	$23.65	$23.70
Purchase #4	$166.38	3.755%	$172.6276	$172.63	$172.65	$172.60
Purchase #5	$53.58	11.278%	$59.6228	$59.62	$59.60	$59.60
Purchase #6	$223.86	11.260%	$249.0666	$249.07	$249.05	$249.10
Purchase #7	$143.53	6.796%	$153.2843	$153.28	$153.30	$153.30
7 purchase totals =	$980.58		$1,054.4165	$1,054.42	$1,054.40	$1,054.50