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	$89.87	6.872%	$96.0459	$96.05	$96.05	$96.00
Purchase #2	$213.44	4.702%	$223.4759	$223.48	$223.50	$223.50
Purchase #3	$9.37	12.659%	$10.5561	$10.56	$10.55	$10.60
Purchase #4	$99.25	4.495%	$103.7113	$103.71	$103.70	$103.70
Purchase #5	$65.60	13.660%	$74.561	$74.56	$74.55	$74.60
Purchase #6	$200.83	13.619%	$228.181	$228.18	$228.20	$228.20
Purchase #7	$104.89	13.821%	$119.3868	$119.39	$119.40	$119.40
7 purchase totals =	$783.25		$855.9180	$855.93	$855.95	$856.00