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	$56.81	11.594%	$63.3966	$63.40	$63.40	$63.40
Purchase #2	$102.72	5.860%	$108.7394	$108.74	$108.75	$108.70
Purchase #3	$57.82	12.808%	$65.2256	$65.23	$65.25	$65.20
Purchase #4	$145.94	13.361%	$165.439	$165.44	$165.45	$165.40
Purchase #5	$88.83	11.705%	$99.2276	$99.23	$99.25	$99.20
Purchase #6	$54.42	3.764%	$56.4684	$56.47	$56.45	$56.50
Purchase #7	$165.61	7.372%	$177.8188	$177.82	$177.80	$177.80
7 purchase totals =	$672.15		$736.3154	$736.33	$736.35	$736.20