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	$39.28	3.639%	$40.7094	$40.71	$40.70	$40.70
Purchase #2	$38.41	10.781%	$42.551	$42.55	$42.55	$42.60
Purchase #3	$168.89	10.597%	$186.7873	$186.79	$186.80	$186.80
Purchase #4	$16.31	11.438%	$18.1755	$18.18	$18.20	$18.20
Purchase #5	$47.83	11.683%	$53.418	$53.42	$53.40	$53.40
Purchase #6	$55.82	8.671%	$60.6602	$60.66	$60.65	$60.70
Purchase #7	$124.99	13.298%	$141.6112	$141.61	$141.60	$141.60
7 purchase totals =	$491.53		$543.9126	$543.92	$543.90	$544.00