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	$141.73	8.860%	$154.2873	$154.29	$154.30	$154.30
Purchase #2	$214.47	13.229%	$242.8422	$242.84	$242.85	$242.80
Purchase #3	$243.76	9.372%	$266.6052	$266.61	$266.60	$266.60
Purchase #4	$180.58	6.750%	$192.7692	$192.77	$192.75	$192.80
Purchase #5	$184.33	6.576%	$196.4515	$196.45	$196.45	$196.50
Purchase #6	$220.44	9.729%	$241.8866	$241.89	$241.90	$241.90
Purchase #7	$183.35	7.408%	$196.9326	$196.93	$196.95	$196.90
7 purchase totals =	$1,368.66		$1,491.7746	$1,491.78	$1,491.80	$1,491.80