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	$195.93	7.500%	$210.6248	$210.62	$210.60	$210.60
Purchase #2	$90.72	11.602%	$101.2453	$101.25	$101.25	$101.20
Purchase #3	$60.81	4.616%	$63.617	$63.62	$63.60	$63.60
Purchase #4	$82.27	8.858%	$89.5575	$89.56	$89.55	$89.60
Purchase #5	$81.49	10.811%	$90.2999	$90.30	$90.30	$90.30
Purchase #6	$249.40	9.310%	$272.6191	$272.62	$272.60	$272.60
Purchase #7	$67.61	11.599%	$75.4521	$75.45	$75.45	$75.50
7 purchase totals =	$828.23		$903.4157	$903.42	$903.35	$903.40