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	$127.25	5.436%	$134.1673	$134.17	$134.15	$134.20
Purchase #2	$52.51	5.658%	$55.481	$55.48	$55.50	$55.50
Purchase #3	$94.71	8.868%	$103.1089	$103.11	$103.10	$103.10
Purchase #4	$244.88	3.660%	$253.8426	$253.84	$253.85	$253.80
Purchase #5	$208.76	6.629%	$222.5987	$222.60	$222.60	$222.60
Purchase #6	$56.81	10.132%	$62.566	$62.57	$62.55	$62.60
Purchase #7	$60.59	7.365%	$65.0525	$65.05	$65.05	$65.10
7 purchase totals =	$845.51		$896.8170	$896.82	$896.80	$896.90