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	$147.44	6.210%	$156.596	$156.60	$156.60	$156.60
Purchase #2	$117.52	5.440%	$123.9131	$123.91	$123.90	$123.90
Purchase #3	$240.76	7.747%	$259.4117	$259.41	$259.40	$259.40
Purchase #4	$160.27	13.463%	$181.8472	$181.85	$181.85	$181.80
Purchase #5	$61.78	7.423%	$66.3659	$66.37	$66.35	$66.40
Purchase #6	$241.29	3.174%	$248.9485	$248.95	$248.95	$248.90
Purchase #7	$172.62	8.865%	$187.9228	$187.92	$187.90	$187.90
7 purchase totals =	$1,141.68		$1,225.0052	$1,225.01	$1,224.95	$1,224.90