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	$80.30	7.591%	$86.3956	$86.40	$86.40	$86.40
Purchase #2	$19.72	5.690%	$20.8421	$20.84	$20.85	$20.80
Purchase #3	$241.84	5.776%	$255.8087	$255.81	$255.80	$255.80
Purchase #4	$222.34	9.679%	$243.8603	$243.86	$243.85	$243.90
Purchase #5	$136.82	5.367%	$144.1631	$144.16	$144.15	$144.20
Purchase #6	$193.25	7.659%	$208.051	$208.05	$208.05	$208.10
Purchase #7	$158.32	3.640%	$164.0828	$164.08	$164.10	$164.10
7 purchase totals =	$1,052.59		$1,123.2036	$1,123.20	$1,123.20	$1,123.30