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	$55.43	7.340%	$59.4986	$59.50	$59.50	$59.50
Purchase #2	$12.81	9.487%	$14.0253	$14.03	$14.05	$14.00
Purchase #3	$18.79	8.611%	$20.408	$20.41	$20.40	$20.40
Purchase #4	$56.28	4.204%	$58.646	$58.65	$58.65	$58.60
Purchase #5	$78.86	9.195%	$86.1112	$86.11	$86.10	$86.10
Purchase #6	$47.42	6.631%	$50.5644	$50.56	$50.55	$50.60
Purchase #7	$141.28	6.585%	$150.5833	$150.58	$150.60	$150.60
7 purchase totals =	$410.87		$439.8368	$439.84	$439.85	$439.80