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	$176.72	13.471%	$200.526	$200.53	$200.55	$200.50
Purchase #2	$186.47	13.189%	$211.0635	$211.06	$211.05	$211.10
Purchase #3	$105.29	7.601%	$113.2931	$113.29	$113.30	$113.30
Purchase #4	$226.69	5.301%	$238.7068	$238.71	$238.70	$238.70
Purchase #5	$159.39	7.388%	$171.1657	$171.17	$171.15	$171.20
Purchase #6	$91.79	11.733%	$102.5597	$102.56	$102.55	$102.60
Purchase #7	$90.76	12.838%	$102.4118	$102.41	$102.40	$102.40
7 purchase totals =	$1,037.11		$1,139.7266	$1,139.73	$1,139.70	$1,139.80