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	$150.68	10.244%	$166.1157	$166.12	$166.10	$166.10
Purchase #2	$150.91	11.321%	$167.9945	$167.99	$168.00	$168.00
Purchase #3	$171.94	10.725%	$190.3806	$190.38	$190.40	$190.40
Purchase #4	$38.59	10.649%	$42.6994	$42.70	$42.70	$42.70
Purchase #5	$171.62	7.445%	$184.3971	$184.40	$184.40	$184.40
Purchase #6	$235.50	7.674%	$253.5723	$253.57	$253.55	$253.60
Purchase #7	$133.71	7.560%	$143.8185	$143.82	$143.80	$143.80
7 purchase totals =	$1,052.95		$1,148.9781	$1,148.98	$1,148.95	$1,149.00