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	$179.56	9.640%	$196.8696	$196.87	$196.85	$196.90
Purchase #2	$68.34	11.378%	$76.1157	$76.12	$76.10	$76.10
Purchase #3	$93.54	7.432%	$100.4919	$100.49	$100.50	$100.50
Purchase #4	$227.55	9.315%	$248.7463	$248.75	$248.75	$248.70
Purchase #5	$119.72	12.410%	$134.5773	$134.58	$134.60	$134.60
Purchase #6	$96.34	11.394%	$107.317	$107.32	$107.30	$107.30
Purchase #7	$128.93	13.463%	$146.2878	$146.29	$146.30	$146.30
7 purchase totals =	$913.98		$1,010.4056	$1,010.42	$1,010.40	$1,010.40