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	$197.61	10.772%	$218.8965	$218.90	$218.90	$218.90
Purchase #2	$146.64	13.819%	$166.9042	$166.90	$166.90	$166.90
Purchase #3	$126.41	3.493%	$130.8255	$130.83	$130.85	$130.80
Purchase #4	$80.69	11.417%	$89.9024	$89.90	$89.90	$89.90
Purchase #5	$167.49	9.685%	$183.7114	$183.71	$183.70	$183.70
Purchase #6	$78.99	5.808%	$83.5777	$83.58	$83.60	$83.60
Purchase #7	$171.36	10.846%	$189.9457	$189.95	$189.95	$189.90
7 purchase totals =	$969.19		$1,063.7634	$1,063.77	$1,063.80	$1,063.70