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	$201.54	5.382%	$212.3869	$212.39	$212.40	$212.40
Purchase #2	$69.70	9.440%	$76.2797	$76.28	$76.30	$76.30
Purchase #3	$29.59	13.589%	$33.611	$33.61	$33.60	$33.60
Purchase #4	$22.72	7.445%	$24.4115	$24.41	$24.40	$24.40
Purchase #5	$154.45	6.758%	$164.8877	$164.89	$164.90	$164.90
Purchase #6	$144.62	5.129%	$152.0376	$152.04	$152.05	$152.00
Purchase #7	$165.59	4.352%	$172.7965	$172.80	$172.80	$172.80
7 purchase totals =	$788.21		$836.4109	$836.42	$836.45	$836.40