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	$45.27	11.839%	$50.6295	$50.63	$50.65	$50.60
Purchase #2	$159.62	5.416%	$168.265	$168.27	$168.25	$168.30
Purchase #3	$118.93	10.573%	$131.5045	$131.50	$131.50	$131.50
Purchase #4	$27.68	9.499%	$30.3093	$30.31	$30.30	$30.30
Purchase #5	$212.64	3.849%	$220.8245	$220.82	$220.80	$220.80
Purchase #6	$92.68	13.784%	$105.455	$105.46	$105.45	$105.50
Purchase #7	$203.32	12.589%	$228.916	$228.92	$228.90	$228.90
7 purchase totals =	$860.14		$935.9038	$935.91	$935.85	$935.90