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	$57.91	13.161%	$65.5315	$65.53	$65.55	$65.50
Purchase #2	$234.95	12.315%	$263.8841	$263.88	$263.90	$263.90
Purchase #3	$11.89	10.639%	$13.155	$13.16	$13.15	$13.20
Purchase #4	$184.85	8.592%	$200.7323	$200.73	$200.75	$200.70
Purchase #5	$17.45	7.315%	$18.7265	$18.73	$18.75	$18.70
Purchase #6	$212.36	13.707%	$241.4682	$241.47	$241.45	$241.50
Purchase #7	$167.39	4.307%	$174.5995	$174.60	$174.60	$174.60
7 purchase totals =	$886.80		$978.0971	$978.10	$978.15	$978.10