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	$122.83	3.618%	$127.274	$127.27	$127.25	$127.30
Purchase #2	$89.94	10.417%	$99.309	$99.31	$99.30	$99.30
Purchase #3	$41.41	6.367%	$44.0466	$44.05	$44.05	$44.00
Purchase #4	$213.61	7.266%	$229.1309	$229.13	$229.15	$229.10
Purchase #5	$108.40	4.787%	$113.5891	$113.59	$113.60	$113.60
Purchase #6	$202.75	6.218%	$215.357	$215.36	$215.35	$215.40
Purchase #7	$133.98	12.766%	$151.0839	$151.08	$151.10	$151.10
7 purchase totals =	$912.92		$979.7905	$979.79	$979.80	$979.80