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	$33.90	5.477%	$35.7567	$35.76	$35.75	$35.80
Purchase #2	$19.79	7.230%	$21.2208	$21.22	$21.20	$21.20
Purchase #3	$167.93	6.569%	$178.9613	$178.96	$178.95	$179.00
Purchase #4	$102.95	8.295%	$111.4897	$111.49	$111.50	$111.50
Purchase #5	$167.89	13.325%	$190.2613	$190.26	$190.25	$190.30
Purchase #6	$222.70	3.743%	$231.0357	$231.04	$231.05	$231.00
Purchase #7	$92.41	3.590%	$95.7275	$95.73	$95.75	$95.70
7 purchase totals =	$807.57		$864.4530	$864.46	$864.45	$864.50