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	$175.40	13.697%	$199.4245	$199.42	$199.40	$199.40
Purchase #2	$35.79	8.511%	$38.8361	$38.84	$38.85	$38.80
Purchase #3	$160.54	11.683%	$179.2959	$179.30	$179.30	$179.30
Purchase #4	$29.86	12.201%	$33.5032	$33.50	$33.50	$33.50
Purchase #5	$54.77	3.535%	$56.7061	$56.71	$56.70	$56.70
Purchase #6	$232.85	8.158%	$251.8459	$251.85	$251.85	$251.80
Purchase #7	$196.28	13.571%	$222.9172	$222.92	$222.90	$222.90
7 purchase totals =	$885.49		$982.5289	$982.54	$982.50	$982.40