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	$69.74	12.105%	$78.182	$78.18	$78.20	$78.20
Purchase #2	$41.92	8.146%	$45.3348	$45.33	$45.35	$45.30
Purchase #3	$212.51	5.251%	$223.6689	$223.67	$223.65	$223.70
Purchase #4	$246.35	10.751%	$272.8351	$272.84	$272.85	$272.80
Purchase #5	$74.32	4.275%	$77.4972	$77.50	$77.50	$77.50
Purchase #6	$248.97	11.417%	$277.3949	$277.39	$277.40	$277.40
Purchase #7	$87.91	5.630%	$92.8593	$92.86	$92.85	$92.90
7 purchase totals =	$981.72		$1,067.7722	$1,067.77	$1,067.80	$1,067.80