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	$92.43	12.826%	$104.2851	$104.29	$104.30	$104.30
Purchase #2	$35.27	5.613%	$37.2497	$37.25	$37.25	$37.20
Purchase #3	$60.54	4.481%	$63.2528	$63.25	$63.25	$63.30
Purchase #4	$11.72	5.660%	$12.3834	$12.38	$12.40	$12.40
Purchase #5	$72.44	11.116%	$80.4924	$80.49	$80.50	$80.50
Purchase #6	$218.90	10.522%	$241.9327	$241.93	$241.95	$241.90
Purchase #7	$244.89	9.577%	$268.3431	$268.34	$268.35	$268.30
7 purchase totals =	$736.19		$807.9392	$807.93	$808.00	$807.90