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	$216.58	7.681%	$233.2155	$233.22	$233.20	$233.20
Purchase #2	$131.48	9.107%	$143.4539	$143.45	$143.45	$143.50
Purchase #3	$98.52	6.159%	$104.5878	$104.59	$104.60	$104.60
Purchase #4	$170.57	6.554%	$181.7492	$181.75	$181.75	$181.70
Purchase #5	$199.72	7.530%	$214.7589	$214.76	$214.75	$214.80
Purchase #6	$118.95	10.858%	$131.8656	$131.87	$131.85	$131.90
Purchase #7	$117.63	13.475%	$133.4806	$133.48	$133.50	$133.50
7 purchase totals =	$1,053.45		$1,143.1115	$1,143.12	$1,143.10	$1,143.20