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	$118.37	8.116%	$127.9769	$127.98	$128.00	$128.00
Purchase #2	$91.52	9.535%	$100.2464	$100.25	$100.25	$100.20
Purchase #3	$94.92	4.508%	$99.199	$99.20	$99.20	$99.20
Purchase #4	$120.96	4.539%	$126.4504	$126.45	$126.45	$126.50
Purchase #5	$213.51	13.143%	$241.5716	$241.57	$241.55	$241.60
Purchase #6	$43.75	12.335%	$49.1466	$49.15	$49.15	$49.10
Purchase #7	$55.34	7.351%	$59.408	$59.41	$59.40	$59.40
7 purchase totals =	$738.37		$803.9989	$804.01	$804.00	$804.00