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	$168.48	7.404%	$180.9543	$180.95	$180.95	$181.00
Purchase #2	$79.52	4.601%	$83.1787	$83.18	$83.20	$83.20
Purchase #3	$14.76	3.814%	$15.3229	$15.32	$15.30	$15.30
Purchase #4	$131.82	11.154%	$146.5232	$146.52	$146.50	$146.50
Purchase #5	$164.54	9.414%	$180.0298	$180.03	$180.05	$180.00
Purchase #6	$140.61	7.800%	$151.5776	$151.58	$151.60	$151.60
Purchase #7	$93.85	13.589%	$106.6033	$106.60	$106.60	$106.60
7 purchase totals =	$793.58		$864.1898	$864.18	$864.20	$864.20