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	$53.51	10.603%	$59.1837	$59.18	$59.20	$59.20
Purchase #2	$84.69	11.234%	$94.2041	$94.20	$94.20	$94.20
Purchase #3	$198.77	5.224%	$209.1537	$209.15	$209.15	$209.20
Purchase #4	$140.77	8.858%	$153.2394	$153.24	$153.25	$153.20
Purchase #5	$176.82	12.481%	$198.8889	$198.89	$198.90	$198.90
Purchase #6	$11.59	12.630%	$13.0538	$13.05	$13.05	$13.10
Purchase #7	$7.28	4.586%	$7.6139	$7.61	$7.60	$7.60
7 purchase totals =	$673.43		$735.3375	$735.32	$735.35	$735.40