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	$123.86	7.614%	$133.2907	$133.29	$133.30	$133.30
Purchase #2	$230.98	4.567%	$241.5289	$241.53	$241.55	$241.50
Purchase #3	$172.25	8.414%	$186.7431	$186.74	$186.75	$186.70
Purchase #4	$156.47	5.207%	$164.6174	$164.62	$164.60	$164.60
Purchase #5	$11.58	6.644%	$12.3494	$12.35	$12.35	$12.30
Purchase #6	$153.97	5.212%	$161.9949	$161.99	$162.00	$162.00
Purchase #7	$196.72	13.314%	$222.9113	$222.91	$222.90	$222.90
7 purchase totals =	$1,045.83		$1,123.4357	$1,123.43	$1,123.45	$1,123.30