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	$187.54	5.289%	$197.459	$197.46	$197.45	$197.50
Purchase #2	$143.85	3.522%	$148.9164	$148.92	$148.90	$148.90
Purchase #3	$160.58	13.787%	$182.7192	$182.72	$182.70	$182.70
Purchase #4	$134.49	12.515%	$151.3214	$151.32	$151.30	$151.30
Purchase #5	$73.53	7.194%	$78.8197	$78.82	$78.80	$78.80
Purchase #6	$164.76	4.531%	$172.2253	$172.23	$172.25	$172.20
Purchase #7	$139.82	4.397%	$145.9679	$145.97	$145.95	$146.00
7 purchase totals =	$1,004.57		$1,077.4289	$1,077.44	$1,077.35	$1,077.40