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	$213.79	4.317%	$223.0193	$223.02	$223.00	$223.00
Purchase #2	$150.88	11.643%	$168.447	$168.45	$168.45	$168.40
Purchase #3	$146.27	11.611%	$163.2534	$163.25	$163.25	$163.30
Purchase #4	$205.51	10.413%	$226.9098	$226.91	$226.90	$226.90
Purchase #5	$52.69	13.303%	$59.6994	$59.70	$59.70	$59.70
Purchase #6	$89.47	7.724%	$96.3807	$96.38	$96.40	$96.40
Purchase #7	$87.45	12.140%	$98.0664	$98.07	$98.05	$98.10
7 purchase totals =	$946.06		$1,035.7760	$1,035.78	$1,035.75	$1,035.80