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	$240.64	10.155%	$265.077	$265.08	$265.10	$265.10
Purchase #2	$64.34	12.750%	$72.5434	$72.54	$72.55	$72.50
Purchase #3	$171.49	13.382%	$194.4388	$194.44	$194.45	$194.40
Purchase #4	$182.33	4.536%	$190.6005	$190.60	$190.60	$190.60
Purchase #5	$63.46	5.602%	$67.015	$67.02	$67.00	$67.00
Purchase #6	$85.71	12.667%	$96.5669	$96.57	$96.55	$96.60
Purchase #7	$226.30	6.158%	$240.2356	$240.24	$240.25	$240.20
7 purchase totals =	$1,034.27		$1,126.4772	$1,126.49	$1,126.50	$1,126.40