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	$147.40	7.832%	$158.9444	$158.94	$158.95	$158.90
Purchase #2	$58.34	12.463%	$65.6109	$65.61	$65.60	$65.60
Purchase #3	$44.41	12.142%	$49.8023	$49.80	$49.80	$49.80
Purchase #4	$85.85	5.223%	$90.3339	$90.33	$90.35	$90.30
Purchase #5	$52.49	6.478%	$55.8903	$55.89	$55.90	$55.90
Purchase #6	$151.64	10.112%	$166.9738	$166.97	$166.95	$167.00
Purchase #7	$86.85	11.611%	$96.9342	$96.93	$96.95	$96.90
7 purchase totals =	$626.98		$684.4898	$684.47	$684.50	$684.40