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	$95.73	11.449%	$106.6901	$106.69	$106.70	$106.70
Purchase #2	$242.61	9.337%	$265.2625	$265.26	$265.25	$265.30
Purchase #3	$39.39	12.383%	$44.2677	$44.27	$44.25	$44.30
Purchase #4	$85.57	5.864%	$90.5878	$90.59	$90.60	$90.60
Purchase #5	$82.42	6.769%	$87.999	$88.00	$88.00	$88.00
Purchase #6	$28.52	9.851%	$31.3295	$31.33	$31.35	$31.30
Purchase #7	$102.84	8.549%	$111.6318	$111.63	$111.65	$111.60
7 purchase totals =	$677.08		$737.7684	$737.77	$737.80	$737.80