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	$6.79	7.134%	$7.2744	$7.27	$7.25	$7.30
Purchase #2	$93.60	7.498%	$100.6181	$100.62	$100.60	$100.60
Purchase #3	$151.55	9.611%	$166.1155	$166.12	$166.10	$166.10
Purchase #4	$224.50	6.848%	$239.8738	$239.87	$239.85	$239.90
Purchase #5	$163.53	5.628%	$172.7335	$172.73	$172.75	$172.70
Purchase #6	$245.61	4.531%	$256.7386	$256.74	$256.75	$256.70
Purchase #7	$133.57	5.466%	$140.8709	$140.87	$140.85	$140.90
7 purchase totals =	$1,019.15		$1,084.2248	$1,084.22	$1,084.15	$1,084.20