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	$77.97	12.190%	$87.4745	$87.47	$87.45	$87.50
Purchase #2	$61.90	13.357%	$70.168	$70.17	$70.15	$70.20
Purchase #3	$213.70	4.759%	$223.87	$223.87	$223.85	$223.90
Purchase #4	$228.85	5.251%	$240.8669	$240.87	$240.85	$240.90
Purchase #5	$161.57	9.783%	$177.3764	$177.38	$177.40	$177.40
Purchase #6	$242.70	9.127%	$264.8512	$264.85	$264.85	$264.90
Purchase #7	$33.34	5.646%	$35.2224	$35.22	$35.20	$35.20
7 purchase totals =	$1,020.03		$1,099.8294	$1,099.83	$1,099.75	$1,100.00