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	$168.89	3.847%	$175.3872	$175.39	$175.40	$175.40
Purchase #2	$37.28	4.171%	$38.8349	$38.83	$38.85	$38.80
Purchase #3	$181.53	4.860%	$190.3524	$190.35	$190.35	$190.40
Purchase #4	$230.25	13.155%	$260.5394	$260.54	$260.55	$260.50
Purchase #5	$188.31	3.345%	$194.609	$194.61	$194.60	$194.60
Purchase #6	$246.84	13.402%	$279.9215	$279.92	$279.90	$279.90
Purchase #7	$235.50	5.736%	$249.0083	$249.01	$249.00	$249.00
7 purchase totals =	$1,288.60		$1,388.6527	$1,388.65	$1,388.65	$1,388.60