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	$118.44	6.730%	$126.411	$126.41	$126.40	$126.40
Purchase #2	$243.45	7.613%	$261.9838	$261.98	$262.00	$262.00
Purchase #3	$38.50	9.709%	$42.238	$42.24	$42.25	$42.20
Purchase #4	$155.76	10.721%	$172.459	$172.46	$172.45	$172.50
Purchase #5	$12.86	6.559%	$13.7035	$13.70	$13.70	$13.70
Purchase #6	$155.92	10.853%	$172.842	$172.84	$172.85	$172.80
Purchase #7	$101.72	8.736%	$110.6063	$110.61	$110.60	$110.60
7 purchase totals =	$826.65		$900.2436	$900.24	$900.25	$900.20