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	$184.82	3.610%	$191.492	$191.49	$191.50	$191.50
Purchase #2	$232.91	8.560%	$252.8471	$252.85	$252.85	$252.80
Purchase #3	$178.79	10.821%	$198.1369	$198.14	$198.15	$198.10
Purchase #4	$216.56	10.285%	$238.8332	$238.83	$238.85	$238.80
Purchase #5	$24.64	9.514%	$26.9842	$26.98	$27.00	$27.00
Purchase #6	$128.89	13.469%	$146.2502	$146.25	$146.25	$146.30
Purchase #7	$172.83	10.233%	$190.5157	$190.52	$190.50	$190.50
7 purchase totals =	$1,139.44		$1,245.0593	$1,245.06	$1,245.10	$1,245.00