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	$124.81	6.593%	$133.0387	$133.04	$133.05	$133.00
Purchase #2	$240.85	10.456%	$266.0333	$266.03	$266.05	$266.00
Purchase #3	$126.40	13.630%	$143.6283	$143.63	$143.65	$143.60
Purchase #4	$39.55	9.859%	$43.4492	$43.45	$43.45	$43.40
Purchase #5	$94.37	5.836%	$99.8774	$99.88	$99.90	$99.90
Purchase #6	$113.67	4.215%	$118.4612	$118.46	$118.45	$118.50
Purchase #7	$102.39	9.312%	$111.9246	$111.92	$111.90	$111.90
7 purchase totals =	$842.04		$916.4127	$916.41	$916.45	$916.30