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	$178.74	11.103%	$198.5855	$198.59	$198.60	$198.60
Purchase #2	$222.89	13.812%	$253.6756	$253.68	$253.70	$253.70
Purchase #3	$148.78	10.618%	$164.5775	$164.58	$164.60	$164.60
Purchase #4	$59.30	5.522%	$62.5745	$62.57	$62.55	$62.60
Purchase #5	$22.69	6.141%	$24.0834	$24.08	$24.10	$24.10
Purchase #6	$157.86	13.679%	$179.4537	$179.45	$179.45	$179.50
Purchase #7	$75.34	3.775%	$78.1841	$78.18	$78.20	$78.20
7 purchase totals =	$865.60		$961.1343	$961.13	$961.20	$961.30