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	$132.94	9.213%	$145.1878	$145.19	$145.20	$145.20
Purchase #2	$40.26	12.837%	$45.4282	$45.43	$45.45	$45.40
Purchase #3	$74.83	6.113%	$79.4044	$79.40	$79.40	$79.40
Purchase #4	$205.73	11.719%	$229.8395	$229.84	$229.85	$229.80
Purchase #5	$219.52	5.439%	$231.4597	$231.46	$231.45	$231.50
Purchase #6	$202.45	7.462%	$217.5568	$217.56	$217.55	$217.60
Purchase #7	$161.27	13.162%	$182.4964	$182.50	$182.50	$182.50
7 purchase totals =	$1,037.00		$1,131.3728	$1,131.38	$1,131.40	$1,131.40