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	$181.50	10.526%	$200.6047	$200.60	$200.60	$200.60
Purchase #2	$168.62	12.270%	$189.3097	$189.31	$189.30	$189.30
Purchase #3	$43.78	12.257%	$49.1461	$49.15	$49.15	$49.10
Purchase #4	$36.45	3.115%	$37.5854	$37.59	$37.60	$37.60
Purchase #5	$79.79	8.868%	$86.8658	$86.87	$86.85	$86.90
Purchase #6	$24.77	13.397%	$28.0884	$28.09	$28.10	$28.10
Purchase #7	$234.85	5.280%	$247.2501	$247.25	$247.25	$247.30
7 purchase totals =	$769.76		$838.8502	$838.86	$838.85	$838.90