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	$187.42	11.280%	$208.561	$208.56	$208.55	$208.60
Purchase #2	$139.27	5.460%	$146.8741	$146.87	$146.85	$146.90
Purchase #3	$34.90	4.498%	$36.4698	$36.47	$36.45	$36.50
Purchase #4	$211.34	3.846%	$219.4681	$219.47	$219.45	$219.50
Purchase #5	$151.43	8.722%	$164.6377	$164.64	$164.65	$164.60
Purchase #6	$52.32	13.560%	$59.4146	$59.41	$59.40	$59.40
Purchase #7	$187.39	5.737%	$198.1406	$198.14	$198.15	$198.10
7 purchase totals =	$964.07		$1,033.5659	$1,033.56	$1,033.50	$1,033.60