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	$63.38	13.843%	$72.1537	$72.15	$72.15	$72.20
Purchase #2	$210.25	9.320%	$229.8453	$229.85	$229.85	$229.80
Purchase #3	$92.95	7.759%	$100.162	$100.16	$100.15	$100.20
Purchase #4	$118.32	13.624%	$134.4399	$134.44	$134.45	$134.40
Purchase #5	$76.46	3.502%	$79.1376	$79.14	$79.15	$79.10
Purchase #6	$208.61	7.431%	$224.1118	$224.11	$224.10	$224.10
Purchase #7	$37.50	13.566%	$42.5873	$42.59	$42.60	$42.60
7 purchase totals =	$807.47		$882.4376	$882.44	$882.45	$882.40