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	$154.47	13.818%	$175.8147	$175.81	$175.80	$175.80
Purchase #2	$81.96	5.687%	$86.6211	$86.62	$86.60	$86.60
Purchase #3	$160.47	7.465%	$172.4491	$172.45	$172.45	$172.40
Purchase #4	$241.56	8.548%	$262.2085	$262.21	$262.20	$262.20
Purchase #5	$191.60	4.658%	$200.5247	$200.52	$200.50	$200.50
Purchase #6	$52.43	7.270%	$56.2417	$56.24	$56.25	$56.20
Purchase #7	$110.48	8.394%	$119.7537	$119.75	$119.75	$119.80
7 purchase totals =	$992.97		$1,073.6135	$1,073.60	$1,073.55	$1,073.50