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	$40.71	12.254%	$45.6986	$45.70	$45.70	$45.70
Purchase #2	$118.89	4.224%	$123.9119	$123.91	$123.90	$123.90
Purchase #3	$5.46	3.705%	$5.6623	$5.66	$5.65	$5.70
Purchase #4	$148.82	10.230%	$164.0443	$164.04	$164.05	$164.00
Purchase #5	$94.61	9.146%	$103.263	$103.26	$103.25	$103.30
Purchase #6	$122.61	4.294%	$127.8749	$127.87	$127.85	$127.90
Purchase #7	$5.65	7.350%	$6.0653	$6.07	$6.05	$6.10
7 purchase totals =	$536.75		$576.5203	$576.51	$576.45	$576.60