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	$55.92	6.353%	$59.4726	$59.47	$59.45	$59.50
Purchase #2	$214.35	12.189%	$240.4771	$240.48	$240.50	$240.50
Purchase #3	$100.56	6.478%	$107.0743	$107.07	$107.05	$107.10
Purchase #4	$182.87	7.512%	$196.6072	$196.61	$196.60	$196.60
Purchase #5	$130.85	6.119%	$138.8567	$138.86	$138.85	$138.90
Purchase #6	$228.92	13.697%	$260.2752	$260.28	$260.30	$260.30
Purchase #7	$73.97	5.524%	$78.0561	$78.06	$78.05	$78.10
7 purchase totals =	$987.44		$1,080.8192	$1,080.83	$1,080.80	$1,081.00