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	$60.89	11.852%	$68.1067	$68.11	$68.10	$68.10
Purchase #2	$115.25	10.180%	$126.9825	$126.98	$127.00	$127.00
Purchase #3	$182.60	4.369%	$190.5778	$190.58	$190.60	$190.60
Purchase #4	$128.39	12.499%	$144.4375	$144.44	$144.45	$144.40
Purchase #5	$159.58	5.774%	$168.7941	$168.79	$168.80	$168.80
Purchase #6	$134.32	11.711%	$150.0502	$150.05	$150.05	$150.10
Purchase #7	$240.28	6.660%	$256.2826	$256.28	$256.30	$256.30
7 purchase totals =	$1,021.31		$1,105.2314	$1,105.23	$1,105.30	$1,105.30