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	$166.83	8.524%	$181.0506	$181.05	$181.05	$181.10
Purchase #2	$84.80	3.789%	$88.0131	$88.01	$88.00	$88.00
Purchase #3	$79.75	5.260%	$83.9449	$83.94	$83.95	$83.90
Purchase #4	$95.31	4.243%	$99.354	$99.35	$99.35	$99.40
Purchase #5	$206.40	5.662%	$218.0864	$218.09	$218.10	$218.10
Purchase #6	$165.97	4.412%	$173.2926	$173.29	$173.30	$173.30
Purchase #7	$100.97	4.874%	$105.8913	$105.89	$105.90	$105.90
7 purchase totals =	$900.03		$949.6329	$949.62	$949.65	$949.70