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	$211.77	13.746%	$240.8799	$240.88	$240.90	$240.90
Purchase #2	$197.61	3.414%	$204.3564	$204.36	$204.35	$204.40
Purchase #3	$57.43	3.864%	$59.6491	$59.65	$59.65	$59.60
Purchase #4	$34.77	4.188%	$36.2262	$36.23	$36.25	$36.20
Purchase #5	$89.83	4.397%	$93.7798	$93.78	$93.80	$93.80
Purchase #6	$176.67	8.581%	$191.8301	$191.83	$191.85	$191.80
Purchase #7	$196.60	5.212%	$206.8468	$206.85	$206.85	$206.80
7 purchase totals =	$964.68		$1,033.5683	$1,033.58	$1,033.65	$1,033.50