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	$83.50	4.298%	$87.0888	$87.09	$87.10	$87.10
Purchase #2	$143.26	13.451%	$162.5299	$162.53	$162.55	$162.50
Purchase #3	$59.70	3.653%	$61.8808	$61.88	$61.90	$61.90
Purchase #4	$173.72	11.754%	$194.139	$194.14	$194.15	$194.10
Purchase #5	$164.81	6.445%	$175.432	$175.43	$175.45	$175.40
Purchase #6	$76.50	12.694%	$86.2109	$86.21	$86.20	$86.20
Purchase #7	$230.86	4.145%	$240.4291	$240.43	$240.45	$240.40
7 purchase totals =	$932.35		$1,007.7105	$1,007.71	$1,007.80	$1,007.60