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	$52.60	5.211%	$55.341	$55.34	$55.35	$55.30
Purchase #2	$162.73	10.497%	$179.8118	$179.81	$179.80	$179.80
Purchase #3	$65.92	6.553%	$70.2397	$70.24	$70.25	$70.20
Purchase #4	$179.41	3.115%	$184.9986	$185.00	$185.00	$185.00
Purchase #5	$209.89	6.213%	$222.9305	$222.93	$222.95	$222.90
Purchase #6	$72.77	10.575%	$80.4654	$80.47	$80.45	$80.50
Purchase #7	$213.31	13.184%	$241.4328	$241.43	$241.45	$241.40
7 purchase totals =	$956.63		$1,035.2198	$1,035.22	$1,035.25	$1,035.10