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	$41.81	4.180%	$43.5577	$43.56	$43.55	$43.60
Purchase #2	$183.51	6.185%	$194.8601	$194.86	$194.85	$194.90
Purchase #3	$9.41	12.671%	$10.6023	$10.60	$10.60	$10.60
Purchase #4	$145.93	3.595%	$151.1762	$151.18	$151.20	$151.20
Purchase #5	$93.84	10.280%	$103.4868	$103.49	$103.50	$103.50
Purchase #6	$216.96	6.757%	$231.62	$231.62	$231.60	$231.60
Purchase #7	$99.73	11.142%	$110.8419	$110.84	$110.85	$110.80
7 purchase totals =	$791.19		$846.1450	$846.15	$846.15	$846.20