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	$11.58	10.504%	$12.7964	$12.80	$12.80	$12.80
Purchase #2	$238.34	5.158%	$250.6336	$250.63	$250.65	$250.60
Purchase #3	$41.39	4.621%	$43.3026	$43.30	$43.30	$43.30
Purchase #4	$218.36	6.720%	$233.0338	$233.03	$233.05	$233.00
Purchase #5	$114.39	7.134%	$122.5506	$122.55	$122.55	$122.60
Purchase #6	$173.92	5.150%	$182.8769	$182.88	$182.90	$182.90
Purchase #7	$200.52	11.341%	$223.261	$223.26	$223.25	$223.30
7 purchase totals =	$998.50		$1,068.4549	$1,068.45	$1,068.50	$1,068.50