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	$54.85	8.759%	$59.6543	$59.65	$59.65	$59.70
Purchase #2	$126.41	8.354%	$136.9703	$136.97	$136.95	$137.00
Purchase #3	$41.63	11.804%	$46.544	$46.54	$46.55	$46.50
Purchase #4	$140.90	7.753%	$151.824	$151.82	$151.80	$151.80
Purchase #5	$235.88	5.622%	$249.1412	$249.14	$249.15	$249.10
Purchase #6	$106.52	3.686%	$110.4463	$110.45	$110.45	$110.40
Purchase #7	$122.72	4.178%	$127.8472	$127.85	$127.85	$127.80
7 purchase totals =	$828.91		$882.4273	$882.42	$882.40	$882.30