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	$11.84	6.542%	$12.6146	$12.61	$12.60	$12.60
Purchase #2	$191.93	6.738%	$204.8622	$204.86	$204.85	$204.90
Purchase #3	$146.49	3.341%	$151.3842	$151.38	$151.40	$151.40
Purchase #4	$16.84	7.661%	$18.1301	$18.13	$18.15	$18.10
Purchase #5	$18.46	8.850%	$20.0937	$20.09	$20.10	$20.10
Purchase #6	$206.73	12.179%	$231.9076	$231.91	$231.90	$231.90
Purchase #7	$241.62	6.331%	$256.917	$256.92	$256.90	$256.90
7 purchase totals =	$833.91		$895.9094	$895.90	$895.90	$895.90