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	$126.25	6.181%	$134.0535	$134.05	$134.05	$134.10
Purchase #2	$38.30	4.191%	$39.9052	$39.91	$39.90	$39.90
Purchase #3	$85.36	6.493%	$90.9024	$90.90	$90.90	$90.90
Purchase #4	$246.87	11.229%	$274.591	$274.59	$274.60	$274.60
Purchase #5	$56.41	12.448%	$63.4319	$63.43	$63.45	$63.40
Purchase #6	$63.72	3.338%	$65.847	$65.85	$65.85	$65.80
Purchase #7	$239.40	10.646%	$264.8865	$264.89	$264.90	$264.90
7 purchase totals =	$856.31		$933.6175	$933.62	$933.65	$933.60