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	$218.55	13.166%	$247.3243	$247.32	$247.30	$247.30
Purchase #2	$158.43	10.708%	$175.3947	$175.39	$175.40	$175.40
Purchase #3	$44.53	8.851%	$48.4714	$48.47	$48.45	$48.50
Purchase #4	$29.93	4.831%	$31.3759	$31.38	$31.40	$31.40
Purchase #5	$241.34	6.231%	$256.3779	$256.38	$256.40	$256.40
Purchase #6	$98.49	3.852%	$102.2838	$102.28	$102.30	$102.30
Purchase #7	$207.52	7.231%	$222.5258	$222.53	$222.55	$222.50
7 purchase totals =	$998.79		$1,083.7538	$1,083.75	$1,083.80	$1,083.80