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	$60.50	7.726%	$65.1742	$65.17	$65.15	$65.20
Purchase #2	$43.76	4.110%	$45.5585	$45.56	$45.55	$45.60
Purchase #3	$98.86	3.522%	$102.3418	$102.34	$102.35	$102.30
Purchase #4	$136.36	5.494%	$143.8516	$143.85	$143.85	$143.90
Purchase #5	$155.99	11.485%	$173.9055	$173.91	$173.90	$173.90
Purchase #6	$45.59	3.383%	$47.1323	$47.13	$47.15	$47.10
Purchase #7	$192.33	4.421%	$200.8329	$200.83	$200.85	$200.80
7 purchase totals =	$733.39		$778.7968	$778.79	$778.80	$778.80