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	$67.60	7.275%	$72.5179	$72.52	$72.50	$72.50
Purchase #2	$244.89	6.720%	$261.3466	$261.35	$261.35	$261.30
Purchase #3	$162.31	4.420%	$169.4841	$169.48	$169.50	$169.50
Purchase #4	$146.57	5.252%	$154.2679	$154.27	$154.25	$154.30
Purchase #5	$193.36	10.479%	$213.6222	$213.62	$213.60	$213.60
Purchase #6	$215.62	10.452%	$238.1566	$238.16	$238.15	$238.20
Purchase #7	$157.54	8.234%	$170.5118	$170.51	$170.50	$170.50
7 purchase totals =	$1,187.89		$1,279.9071	$1,279.91	$1,279.85	$1,279.90