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	$179.39	4.302%	$187.1074	$187.11	$187.10	$187.10
Purchase #2	$126.60	13.823%	$144.0999	$144.10	$144.10	$144.10
Purchase #3	$25.58	10.643%	$28.3025	$28.30	$28.30	$28.30
Purchase #4	$100.96	3.505%	$104.4986	$104.50	$104.50	$104.50
Purchase #5	$150.69	11.421%	$167.9003	$167.90	$167.90	$167.90
Purchase #6	$132.71	9.833%	$145.7594	$145.76	$145.75	$145.80
Purchase #7	$147.83	11.346%	$164.6028	$164.60	$164.60	$164.60
7 purchase totals =	$863.76		$942.2709	$942.27	$942.25	$942.30