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	$142.47	5.780%	$150.7048	$150.70	$150.70	$150.70
Purchase #2	$6.80	11.561%	$7.5861	$7.59	$7.60	$7.60
Purchase #3	$188.90	10.772%	$209.2483	$209.25	$209.25	$209.20
Purchase #4	$178.25	6.320%	$189.5154	$189.52	$189.50	$189.50
Purchase #5	$119.62	6.611%	$127.5281	$127.53	$127.55	$127.50
Purchase #6	$108.33	10.116%	$119.2887	$119.29	$119.30	$119.30
Purchase #7	$18.92	5.622%	$19.9837	$19.98	$20.00	$20.00
7 purchase totals =	$763.29		$823.8551	$823.86	$823.90	$823.80