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	$104.42	11.463%	$116.3897	$116.39	$116.40	$116.40
Purchase #2	$103.84	8.227%	$112.3829	$112.38	$112.40	$112.40
Purchase #3	$50.85	8.300%	$55.0706	$55.07	$55.05	$55.10
Purchase #4	$110.68	3.599%	$114.6634	$114.66	$114.65	$114.70
Purchase #5	$53.55	10.560%	$59.2049	$59.20	$59.20	$59.20
Purchase #6	$156.50	5.296%	$164.7882	$164.79	$164.80	$164.80
Purchase #7	$157.37	13.751%	$179.0099	$179.01	$179.00	$179.00
7 purchase totals =	$737.21		$801.5096	$801.50	$801.50	$801.60