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	$167.78	11.459%	$187.0059	$187.01	$187.00	$187.00
Purchase #2	$10.49	12.214%	$11.7712	$11.77	$11.75	$11.80
Purchase #3	$191.53	6.510%	$203.9986	$204.00	$204.00	$204.00
Purchase #4	$164.34	10.352%	$181.3525	$181.35	$181.35	$181.40
Purchase #5	$211.94	5.509%	$223.6158	$223.62	$223.60	$223.60
Purchase #6	$209.69	6.785%	$223.9175	$223.92	$223.90	$223.90
Purchase #7	$172.93	10.373%	$190.868	$190.87	$190.85	$190.90
7 purchase totals =	$1,128.70		$1,222.5295	$1,222.54	$1,222.45	$1,222.60