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	$151.66	6.435%	$161.4193	$161.42	$161.40	$161.40
Purchase #2	$182.87	8.281%	$198.0135	$198.01	$198.00	$198.00
Purchase #3	$73.27	11.179%	$81.4609	$81.46	$81.45	$81.50
Purchase #4	$38.47	13.172%	$43.5373	$43.54	$43.55	$43.50
Purchase #5	$97.97	11.742%	$109.4736	$109.47	$109.45	$109.50
Purchase #6	$109.67	6.593%	$116.9005	$116.90	$116.90	$116.90
Purchase #7	$43.77	6.466%	$46.6002	$46.60	$46.60	$46.60
7 purchase totals =	$697.68		$757.4053	$757.40	$757.35	$757.40