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	$154.45	8.610%	$167.7481	$167.75	$167.75	$167.70
Purchase #2	$179.35	10.624%	$198.4041	$198.40	$198.40	$198.40
Purchase #3	$126.48	4.839%	$132.6004	$132.60	$132.60	$132.60
Purchase #4	$144.43	4.299%	$150.639	$150.64	$150.65	$150.60
Purchase #5	$77.84	9.858%	$85.5135	$85.51	$85.50	$85.50
Purchase #6	$79.93	13.367%	$90.6142	$90.61	$90.60	$90.60
Purchase #7	$243.77	10.560%	$269.5121	$269.51	$269.50	$269.50
7 purchase totals =	$1,006.25		$1,095.0314	$1,095.02	$1,095.00	$1,094.90