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	$179.59	9.573%	$196.7822	$196.78	$196.80	$196.80
Purchase #2	$114.54	4.304%	$119.4698	$119.47	$119.45	$119.50
Purchase #3	$195.26	3.390%	$201.8793	$201.88	$201.90	$201.90
Purchase #4	$128.71	13.491%	$146.0743	$146.07	$146.05	$146.10
Purchase #5	$242.40	10.148%	$266.9988	$267.00	$267.00	$267.00
Purchase #6	$28.61	11.114%	$31.7897	$31.79	$31.80	$31.80
Purchase #7	$183.77	8.736%	$199.8241	$199.82	$199.80	$199.80
7 purchase totals =	$1,072.88		$1,162.8182	$1,162.81	$1,162.80	$1,162.90