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	$41.93	3.662%	$43.4655	$43.47	$43.45	$43.50
Purchase #2	$191.73	13.167%	$216.9751	$216.98	$217.00	$217.00
Purchase #3	$42.29	12.408%	$47.5373	$47.54	$47.55	$47.50
Purchase #4	$196.81	12.329%	$221.0747	$221.07	$221.05	$221.10
Purchase #5	$85.67	4.307%	$89.3598	$89.36	$89.35	$89.40
Purchase #6	$202.25	3.784%	$209.9031	$209.90	$209.90	$209.90
Purchase #7	$73.42	8.798%	$79.8795	$79.88	$79.90	$79.90
7 purchase totals =	$834.10		$908.1950	$908.20	$908.20	$908.30