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	$99.40	11.813%	$111.1421	$111.14	$111.15	$111.10
Purchase #2	$73.28	11.679%	$81.8384	$81.84	$81.85	$81.80
Purchase #3	$172.96	3.738%	$179.4252	$179.43	$179.45	$179.40
Purchase #4	$225.70	13.156%	$255.3931	$255.39	$255.40	$255.40
Purchase #5	$161.29	7.225%	$172.9432	$172.94	$172.95	$172.90
Purchase #6	$192.46	12.839%	$217.1699	$217.17	$217.15	$217.20
Purchase #7	$92.95	13.753%	$105.7334	$105.73	$105.75	$105.70
7 purchase totals =	$1,018.04		$1,123.6453	$1,123.64	$1,123.70	$1,123.50