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	$59.47	8.610%	$64.5904	$64.59	$64.60	$64.60
Purchase #2	$57.46	7.637%	$61.8482	$61.85	$61.85	$61.80
Purchase #3	$241.46	7.605%	$259.823	$259.82	$259.80	$259.80
Purchase #4	$182.83	9.661%	$200.4932	$200.49	$200.50	$200.50
Purchase #5	$107.56	5.174%	$113.1252	$113.13	$113.15	$113.10
Purchase #6	$182.72	9.793%	$200.6138	$200.61	$200.60	$200.60
Purchase #7	$200.25	13.206%	$226.695	$226.70	$226.70	$226.70
7 purchase totals =	$1,031.75		$1,127.1888	$1,127.19	$1,127.20	$1,127.10