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	$158.79	4.779%	$166.3786	$166.38	$166.40	$166.40
Purchase #2	$196.81	10.853%	$218.1698	$218.17	$218.15	$218.20
Purchase #3	$247.89	3.710%	$257.0867	$257.09	$257.10	$257.10
Purchase #4	$42.41	7.626%	$45.6442	$45.64	$45.65	$45.60
Purchase #5	$91.86	12.283%	$103.1432	$103.14	$103.15	$103.10
Purchase #6	$224.49	4.646%	$234.9198	$234.92	$234.90	$234.90
Purchase #7	$34.48	4.410%	$36.0006	$36.00	$36.00	$36.00
7 purchase totals =	$996.73		$1,061.3429	$1,061.34	$1,061.35	$1,061.30