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	$125.81	13.229%	$142.4534	$142.45	$142.45	$142.50
Purchase #2	$141.75	5.130%	$149.0218	$149.02	$149.00	$149.00
Purchase #3	$60.60	11.250%	$67.4175	$67.42	$67.40	$67.40
Purchase #4	$119.63	3.606%	$123.9439	$123.94	$123.95	$123.90
Purchase #5	$128.72	4.816%	$134.9192	$134.92	$134.90	$134.90
Purchase #6	$126.79	11.837%	$141.7981	$141.80	$141.80	$141.80
Purchase #7	$43.60	6.352%	$46.3695	$46.37	$46.35	$46.40
7 purchase totals =	$746.90		$805.9234	$805.92	$805.85	$805.90