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	$183.26	11.325%	$204.0142	$204.01	$204.00	$204.00
Purchase #2	$72.84	7.780%	$78.507	$78.51	$78.50	$78.50
Purchase #3	$118.76	8.162%	$128.4532	$128.45	$128.45	$128.50
Purchase #4	$116.84	5.675%	$123.4707	$123.47	$123.45	$123.50
Purchase #5	$47.77	13.545%	$54.2404	$54.24	$54.25	$54.20
Purchase #6	$177.57	11.131%	$197.3353	$197.34	$197.35	$197.30
Purchase #7	$246.46	12.174%	$276.464	$276.46	$276.45	$276.50
7 purchase totals =	$963.50		$1,062.4848	$1,062.48	$1,062.45	$1,062.50