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	$215.62	12.410%	$242.3784	$242.38	$242.40	$242.40
Purchase #2	$52.97	3.854%	$55.0115	$55.01	$55.00	$55.00
Purchase #3	$149.91	10.340%	$165.4107	$165.41	$165.40	$165.40
Purchase #4	$56.52	7.721%	$60.8839	$60.88	$60.90	$60.90
Purchase #5	$139.89	11.423%	$155.8696	$155.87	$155.85	$155.90
Purchase #6	$217.28	12.584%	$244.6225	$244.62	$244.60	$244.60
Purchase #7	$83.54	7.798%	$90.0544	$90.05	$90.05	$90.10
7 purchase totals =	$915.73		$1,014.2310	$1,014.22	$1,014.20	$1,014.30