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	$136.99	10.543%	$151.4329	$151.43	$151.45	$151.40
Purchase #2	$139.79	3.413%	$144.561	$144.56	$144.55	$144.60
Purchase #3	$213.61	12.360%	$240.0122	$240.01	$240.00	$240.00
Purchase #4	$208.98	8.217%	$226.1519	$226.15	$226.15	$226.20
Purchase #5	$155.63	4.334%	$162.375	$162.38	$162.40	$162.40
Purchase #6	$95.91	12.105%	$107.5199	$107.52	$107.50	$107.50
Purchase #7	$122.42	4.449%	$127.8665	$127.87	$127.85	$127.90
7 purchase totals =	$1,073.33		$1,159.9194	$1,159.92	$1,159.90	$1,160.00