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	$184.47	6.638%	$196.7151	$196.72	$196.70	$196.70
Purchase #2	$250.49	5.833%	$265.1011	$265.10	$265.10	$265.10
Purchase #3	$218.29	11.127%	$242.5791	$242.58	$242.60	$242.60
Purchase #4	$48.86	9.494%	$53.4988	$53.50	$53.50	$53.50
Purchase #5	$117.47	4.106%	$122.2933	$122.29	$122.30	$122.30
Purchase #6	$52.66	7.774%	$56.7538	$56.75	$56.75	$56.80
Purchase #7	$94.76	9.536%	$103.7963	$103.80	$103.80	$103.80
7 purchase totals =	$967.00		$1,040.7375	$1,040.74	$1,040.75	$1,040.80