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	$59.75	10.136%	$65.8063	$65.81	$65.80	$65.80
Purchase #2	$93.50	10.172%	$103.0108	$103.01	$103.00	$103.00
Purchase #3	$85.57	13.258%	$96.9149	$96.91	$96.90	$96.90
Purchase #4	$158.52	9.586%	$173.7157	$173.72	$173.70	$173.70
Purchase #5	$243.90	13.200%	$276.0948	$276.09	$276.10	$276.10
Purchase #6	$237.92	9.858%	$261.3742	$261.37	$261.35	$261.40
Purchase #7	$11.69	6.817%	$12.4869	$12.49	$12.50	$12.50
7 purchase totals =	$890.85		$989.4036	$989.40	$989.35	$989.40