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	$139.42	3.866%	$144.81	$144.81	$144.80	$144.80
Purchase #2	$38.88	10.373%	$42.913	$42.91	$42.90	$42.90
Purchase #3	$34.52	9.772%	$37.8933	$37.89	$37.90	$37.90
Purchase #4	$230.96	6.224%	$245.335	$245.34	$245.35	$245.30
Purchase #5	$113.96	3.465%	$117.9087	$117.91	$117.90	$117.90
Purchase #6	$78.58	12.486%	$88.3915	$88.39	$88.40	$88.40
Purchase #7	$52.85	11.682%	$59.0239	$59.02	$59.00	$59.00
7 purchase totals =	$689.17		$736.2754	$736.27	$736.25	$736.20