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	$11.71	12.118%	$13.129	$13.13	$13.15	$13.10
Purchase #2	$74.74	4.407%	$78.0338	$78.03	$78.05	$78.00
Purchase #3	$18.57	10.272%	$20.4775	$20.48	$20.50	$20.50
Purchase #4	$38.85	8.147%	$42.0151	$42.02	$42.00	$42.00
Purchase #5	$34.41	9.377%	$37.6366	$37.64	$37.65	$37.60
Purchase #6	$72.88	4.384%	$76.0751	$76.08	$76.10	$76.10
Purchase #7	$182.92	5.496%	$192.9733	$192.97	$192.95	$193.00
7 purchase totals =	$434.08		$460.3404	$460.35	$460.40	$460.30