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	$98.28	3.763%	$101.9783	$101.98	$102.00	$102.00
Purchase #2	$106.51	4.588%	$111.3967	$111.40	$111.40	$111.40
Purchase #3	$187.86	9.664%	$206.0148	$206.01	$206.00	$206.00
Purchase #4	$208.28	12.765%	$234.8669	$234.87	$234.85	$234.90
Purchase #5	$167.93	13.492%	$190.5871	$190.59	$190.60	$190.60
Purchase #6	$95.99	9.212%	$104.8326	$104.83	$104.85	$104.80
Purchase #7	$64.94	10.373%	$71.6762	$71.68	$71.70	$71.70
7 purchase totals =	$929.79		$1,021.3526	$1,021.36	$1,021.40	$1,021.40