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	$127.36	12.222%	$142.9259	$142.93	$142.95	$142.90
Purchase #2	$31.64	4.741%	$33.1401	$33.14	$33.15	$33.10
Purchase #3	$18.58	6.830%	$19.849	$19.85	$19.85	$19.80
Purchase #4	$20.60	10.117%	$22.6841	$22.68	$22.70	$22.70
Purchase #5	$150.43	12.278%	$168.8998	$168.90	$168.90	$168.90
Purchase #6	$143.44	8.124%	$155.0931	$155.09	$155.10	$155.10
Purchase #7	$137.39	4.159%	$143.1041	$143.10	$143.10	$143.10
7 purchase totals =	$629.44		$685.6961	$685.69	$685.75	$685.60