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	$112.51	3.673%	$116.6425	$116.64	$116.65	$116.60
Purchase #2	$227.42	13.549%	$258.2331	$258.23	$258.25	$258.20
Purchase #3	$141.85	7.198%	$152.0604	$152.06	$152.05	$152.10
Purchase #4	$101.49	3.473%	$105.0147	$105.01	$105.00	$105.00
Purchase #5	$135.93	6.550%	$144.8334	$144.83	$144.85	$144.80
Purchase #6	$37.86	12.694%	$42.6659	$42.67	$42.65	$42.70
Purchase #7	$222.67	10.491%	$246.0303	$246.03	$246.05	$246.00
7 purchase totals =	$979.73		$1,065.4803	$1,065.47	$1,065.50	$1,065.40