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	$168.51	11.339%	$187.6173	$187.62	$187.60	$187.60
Purchase #2	$105.43	9.406%	$115.3467	$115.35	$115.35	$115.30
Purchase #3	$149.31	11.109%	$165.8968	$165.90	$165.90	$165.90
Purchase #4	$28.75	11.312%	$32.0022	$32.00	$32.00	$32.00
Purchase #5	$14.33	10.345%	$15.8124	$15.81	$15.80	$15.80
Purchase #6	$46.38	4.167%	$48.3127	$48.31	$48.30	$48.30
Purchase #7	$103.34	6.283%	$109.8329	$109.83	$109.85	$109.80
7 purchase totals =	$616.05		$674.8210	$674.82	$674.80	$674.70