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	$142.36	4.565%	$148.8587	$148.86	$148.85	$148.90
Purchase #2	$181.39	4.163%	$188.9413	$188.94	$188.95	$188.90
Purchase #3	$24.44	12.325%	$27.4522	$27.45	$27.45	$27.50
Purchase #4	$44.78	13.454%	$50.8047	$50.80	$50.80	$50.80
Purchase #5	$37.38	13.413%	$42.3938	$42.39	$42.40	$42.40
Purchase #6	$222.72	8.391%	$241.4084	$241.41	$241.40	$241.40
Purchase #7	$10.68	12.221%	$11.9852	$11.99	$12.00	$12.00
7 purchase totals =	$663.75		$711.8443	$711.84	$711.85	$711.90