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	$200.49	12.745%	$226.0425	$226.04	$226.05	$226.00
Purchase #2	$132.39	13.669%	$150.4864	$150.49	$150.50	$150.50
Purchase #3	$172.96	9.612%	$189.5849	$189.58	$189.60	$189.60
Purchase #4	$223.43	10.399%	$246.6645	$246.66	$246.65	$246.70
Purchase #5	$52.70	12.563%	$59.3207	$59.32	$59.30	$59.30
Purchase #6	$110.70	5.500%	$116.7885	$116.79	$116.80	$116.80
Purchase #7	$12.60	12.508%	$14.176	$14.18	$14.20	$14.20
7 purchase totals =	$905.27		$1,003.0635	$1,003.06	$1,003.10	$1,003.10