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	$182.67	8.298%	$197.828	$197.83	$197.85	$197.80
Purchase #2	$172.34	6.719%	$183.9195	$183.92	$183.90	$183.90
Purchase #3	$59.59	10.388%	$65.7802	$65.78	$65.80	$65.80
Purchase #4	$7.50	5.772%	$7.9329	$7.93	$7.95	$7.90
Purchase #5	$95.39	5.543%	$100.6775	$100.68	$100.70	$100.70
Purchase #6	$52.53	10.160%	$57.867	$57.87	$57.85	$57.90
Purchase #7	$218.33	4.807%	$228.8251	$228.83	$228.85	$228.80
7 purchase totals =	$788.35		$842.8302	$842.84	$842.90	$842.80