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	$144.30	6.469%	$153.6348	$153.63	$153.65	$153.60
Purchase #2	$244.59	12.360%	$274.8213	$274.82	$274.80	$274.80
Purchase #3	$173.80	13.228%	$196.7903	$196.79	$196.80	$196.80
Purchase #4	$88.41	13.545%	$100.3851	$100.39	$100.40	$100.40
Purchase #5	$147.71	9.125%	$161.1885	$161.19	$161.20	$161.20
Purchase #6	$31.84	3.543%	$32.9681	$32.97	$32.95	$33.00
Purchase #7	$212.38	11.158%	$236.0774	$236.08	$236.10	$236.10
7 purchase totals =	$1,043.03		$1,155.8655	$1,155.87	$1,155.90	$1,155.90