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	$78.26	9.721%	$85.8677	$85.87	$85.85	$85.90
Purchase #2	$13.56	12.864%	$15.3044	$15.30	$15.30	$15.30
Purchase #3	$167.69	13.640%	$190.5629	$190.56	$190.55	$190.60
Purchase #4	$118.51	3.437%	$122.5832	$122.58	$122.60	$122.60
Purchase #5	$20.31	5.225%	$21.3712	$21.37	$21.35	$21.40
Purchase #6	$172.35	10.133%	$189.8142	$189.81	$189.80	$189.80
Purchase #7	$152.59	9.722%	$167.4248	$167.42	$167.40	$167.40
7 purchase totals =	$723.27		$792.9284	$792.91	$792.85	$793.00