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	$61.25	10.720%	$67.816	$67.82	$67.80	$67.80
Purchase #2	$156.57	9.161%	$170.9134	$170.91	$170.90	$170.90
Purchase #3	$205.90	8.109%	$222.5964	$222.60	$222.60	$222.60
Purchase #4	$83.37	10.678%	$92.2722	$92.27	$92.25	$92.30
Purchase #5	$35.95	10.303%	$39.6539	$39.65	$39.65	$39.70
Purchase #6	$93.71	9.837%	$102.9283	$102.93	$102.95	$102.90
Purchase #7	$35.82	7.795%	$38.6122	$38.61	$38.60	$38.60
7 purchase totals =	$672.57		$734.7924	$734.79	$734.75	$734.80