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	$200.67	8.730%	$218.1885	$218.19	$218.20	$218.20
Purchase #2	$138.60	4.535%	$144.8855	$144.89	$144.90	$144.90
Purchase #3	$221.81	13.507%	$251.7699	$251.77	$251.75	$251.80
Purchase #4	$18.61	8.361%	$20.166	$20.17	$20.15	$20.20
Purchase #5	$115.89	12.774%	$130.6938	$130.69	$130.70	$130.70
Purchase #6	$122.92	4.470%	$128.4145	$128.41	$128.40	$128.40
Purchase #7	$106.91	4.660%	$111.892	$111.89	$111.90	$111.90
7 purchase totals =	$925.41		$1,006.0102	$1,006.01	$1,006.00	$1,006.10