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	$169.27	12.343%	$190.163	$190.16	$190.15	$190.20
Purchase #2	$31.52	4.801%	$33.0333	$33.03	$33.05	$33.00
Purchase #3	$157.37	4.593%	$164.598	$164.60	$164.60	$164.60
Purchase #4	$119.37	8.435%	$129.4389	$129.44	$129.45	$129.40
Purchase #5	$161.62	3.434%	$167.17	$167.17	$167.15	$167.20
Purchase #6	$146.71	4.689%	$153.5892	$153.59	$153.60	$153.60
Purchase #7	$50.61	11.257%	$56.3072	$56.31	$56.30	$56.30
7 purchase totals =	$836.47		$894.2996	$894.30	$894.30	$894.30