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	$42.52	13.452%	$48.2398	$48.24	$48.25	$48.20
Purchase #2	$109.40	6.575%	$116.5931	$116.59	$116.60	$116.60
Purchase #3	$112.66	6.300%	$119.7576	$119.76	$119.75	$119.80
Purchase #4	$15.69	11.117%	$17.4343	$17.43	$17.45	$17.40
Purchase #5	$215.64	6.130%	$228.8587	$228.86	$228.85	$228.90
Purchase #6	$28.87	13.117%	$32.6569	$32.66	$32.65	$32.70
Purchase #7	$208.63	6.556%	$222.3078	$222.31	$222.30	$222.30
7 purchase totals =	$733.41		$785.8482	$785.85	$785.85	$785.90