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	$237.88	9.231%	$259.8387	$259.84	$259.85	$259.80
Purchase #2	$120.37	4.702%	$126.0298	$126.03	$126.05	$126.00
Purchase #3	$214.46	13.202%	$242.773	$242.77	$242.75	$242.80
Purchase #4	$30.86	3.337%	$31.8898	$31.89	$31.90	$31.90
Purchase #5	$144.62	3.241%	$149.3071	$149.31	$149.30	$149.30
Purchase #6	$247.86	10.338%	$273.4838	$273.48	$273.50	$273.50
Purchase #7	$116.37	9.300%	$127.1924	$127.19	$127.20	$127.20
7 purchase totals =	$1,112.42		$1,210.5146	$1,210.51	$1,210.55	$1,210.50