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	$15.38	9.197%	$16.7945	$16.79	$16.80	$16.80
Purchase #2	$19.93	4.353%	$20.7976	$20.80	$20.80	$20.80
Purchase #3	$56.41	13.764%	$64.1743	$64.17	$64.15	$64.20
Purchase #4	$162.46	11.129%	$180.5402	$180.54	$180.55	$180.50
Purchase #5	$80.35	11.824%	$89.8506	$89.85	$89.85	$89.90
Purchase #6	$14.56	7.153%	$15.6015	$15.60	$15.60	$15.60
Purchase #7	$174.69	3.409%	$180.6452	$180.65	$180.65	$180.60
7 purchase totals =	$523.78		$568.4039	$568.40	$568.40	$568.40