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	$209.40	6.210%	$222.4037	$222.40	$222.40	$222.40
Purchase #2	$87.53	5.214%	$92.0938	$92.09	$92.10	$92.10
Purchase #3	$184.56	4.119%	$192.162	$192.16	$192.15	$192.20
Purchase #4	$180.38	6.310%	$191.762	$191.76	$191.75	$191.80
Purchase #5	$136.41	6.594%	$145.4049	$145.40	$145.40	$145.40
Purchase #6	$122.52	4.187%	$127.6499	$127.65	$127.65	$127.60
Purchase #7	$100.76	8.644%	$109.4697	$109.47	$109.45	$109.50
7 purchase totals =	$1,021.56		$1,080.9460	$1,080.93	$1,080.90	$1,081.00