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	$129.31	4.128%	$134.6479	$134.65	$134.65	$134.60
Purchase #2	$203.48	9.225%	$222.251	$222.25	$222.25	$222.30
Purchase #3	$232.66	10.204%	$256.4006	$256.40	$256.40	$256.40
Purchase #4	$160.39	3.527%	$166.047	$166.05	$166.05	$166.00
Purchase #5	$89.65	12.481%	$100.8392	$100.84	$100.85	$100.80
Purchase #6	$26.42	4.332%	$27.5645	$27.56	$27.55	$27.60
Purchase #7	$52.91	12.301%	$59.4185	$59.42	$59.40	$59.40
7 purchase totals =	$894.82		$967.1687	$967.17	$967.15	$967.10