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	$89.82	13.705%	$102.1298	$102.13	$102.15	$102.10
Purchase #2	$190.56	9.224%	$208.1373	$208.14	$208.15	$208.10
Purchase #3	$157.53	11.253%	$175.2569	$175.26	$175.25	$175.30
Purchase #4	$82.38	10.163%	$90.7523	$90.75	$90.75	$90.80
Purchase #5	$226.70	13.196%	$256.6153	$256.62	$256.60	$256.60
Purchase #6	$62.50	13.108%	$70.6925	$70.69	$70.70	$70.70
Purchase #7	$152.88	12.481%	$171.961	$171.96	$171.95	$172.00
7 purchase totals =	$962.37		$1,075.5451	$1,075.55	$1,075.55	$1,075.60