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	$180.30	7.850%	$194.4536	$194.45	$194.45	$194.50
Purchase #2	$103.33	9.635%	$113.2858	$113.29	$113.30	$113.30
Purchase #3	$108.60	9.590%	$119.0147	$119.01	$119.00	$119.00
Purchase #4	$146.79	9.630%	$160.9259	$160.93	$160.95	$160.90
Purchase #5	$162.89	5.825%	$172.3783	$172.38	$172.40	$172.40
Purchase #6	$60.29	10.465%	$66.5993	$66.60	$66.60	$66.60
Purchase #7	$193.88	5.814%	$205.1522	$205.15	$205.15	$205.20
7 purchase totals =	$956.08		$1,031.8098	$1,031.81	$1,031.85	$1,031.90