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	$215.36	12.118%	$241.4573	$241.46	$241.45	$241.50
Purchase #2	$248.64	12.578%	$279.9139	$279.91	$279.90	$279.90
Purchase #3	$180.66	7.308%	$193.8626	$193.86	$193.85	$193.90
Purchase #4	$37.65	12.842%	$42.485	$42.49	$42.50	$42.50
Purchase #5	$57.76	4.375%	$60.287	$60.29	$60.30	$60.30
Purchase #6	$152.77	8.241%	$165.3598	$165.36	$165.35	$165.40
Purchase #7	$76.31	9.561%	$83.606	$83.61	$83.60	$83.60
7 purchase totals =	$969.15		$1,066.9716	$1,066.98	$1,066.95	$1,067.10