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	$185.26	11.475%	$206.5186	$206.52	$206.50	$206.50
Purchase #2	$88.33	12.151%	$99.063	$99.06	$99.05	$99.10
Purchase #3	$241.52	5.210%	$254.1032	$254.10	$254.10	$254.10
Purchase #4	$5.84	12.762%	$6.5853	$6.59	$6.60	$6.60
Purchase #5	$208.59	5.437%	$219.931	$219.93	$219.95	$219.90
Purchase #6	$172.87	4.654%	$180.9154	$180.92	$180.90	$180.90
Purchase #7	$31.99	7.457%	$34.3755	$34.38	$34.40	$34.40
7 purchase totals =	$934.40		$1,001.4920	$1,001.50	$1,001.50	$1,001.50