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	$30.40	10.575%	$33.6148	$33.61	$33.60	$33.60
Purchase #2	$105.69	3.737%	$109.6396	$109.64	$109.65	$109.60
Purchase #3	$11.69	12.359%	$13.1348	$13.13	$13.15	$13.10
Purchase #4	$135.49	12.492%	$152.4154	$152.42	$152.40	$152.40
Purchase #5	$105.92	13.532%	$120.2531	$120.25	$120.25	$120.30
Purchase #6	$76.34	13.615%	$86.7337	$86.73	$86.75	$86.70
Purchase #7	$171.28	6.406%	$182.2522	$182.25	$182.25	$182.30
7 purchase totals =	$636.81		$698.0436	$698.03	$698.05	$698.00