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	$232.38	13.799%	$264.4461	$264.45	$264.45	$264.40
Purchase #2	$179.80	11.462%	$200.4087	$200.41	$200.40	$200.40
Purchase #3	$249.77	6.848%	$266.8742	$266.87	$266.85	$266.90
Purchase #4	$226.39	11.153%	$251.6393	$251.64	$251.65	$251.60
Purchase #5	$24.73	3.417%	$25.575	$25.58	$25.60	$25.60
Purchase #6	$74.70	9.801%	$82.0213	$82.02	$82.00	$82.00
Purchase #7	$16.59	9.510%	$18.1677	$18.17	$18.15	$18.20
7 purchase totals =	$1,004.36		$1,109.1323	$1,109.14	$1,109.10	$1,109.10