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	$155.82	8.230%	$168.644	$168.64	$168.65	$168.60
Purchase #2	$249.74	5.105%	$262.4892	$262.49	$262.50	$262.50
Purchase #3	$159.77	12.392%	$179.5687	$179.57	$179.55	$179.60
Purchase #4	$12.56	4.825%	$13.166	$13.17	$13.15	$13.20
Purchase #5	$231.41	12.400%	$260.1048	$260.10	$260.10	$260.10
Purchase #6	$55.98	13.153%	$63.343	$63.34	$63.35	$63.30
Purchase #7	$139.96	8.782%	$152.2513	$152.25	$152.25	$152.30
7 purchase totals =	$1,005.24		$1,099.5670	$1,099.56	$1,099.55	$1,099.60