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	$43.45	10.175%	$47.871	$47.87	$47.85	$47.90
Purchase #2	$150.54	13.507%	$170.8734	$170.87	$170.85	$170.90
Purchase #3	$124.43	7.716%	$134.031	$134.03	$134.05	$134.00
Purchase #4	$159.52	7.710%	$171.819	$171.82	$171.80	$171.80
Purchase #5	$83.36	11.317%	$92.7939	$92.79	$92.80	$92.80
Purchase #6	$51.61	11.321%	$57.4528	$57.45	$57.45	$57.50
Purchase #7	$40.77	6.459%	$43.4033	$43.40	$43.40	$43.40
7 purchase totals =	$653.68		$718.2444	$718.23	$718.20	$718.30