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	$69.65	3.440%	$72.046	$72.05	$72.05	$72.00
Purchase #2	$108.37	10.601%	$119.8583	$119.86	$119.85	$119.90
Purchase #3	$90.58	5.319%	$95.398	$95.40	$95.40	$95.40
Purchase #4	$163.79	7.761%	$176.5017	$176.50	$176.50	$176.50
Purchase #5	$228.57	3.282%	$236.0717	$236.07	$236.05	$236.10
Purchase #6	$46.48	12.648%	$52.3588	$52.36	$52.35	$52.40
Purchase #7	$83.95	6.471%	$89.3824	$89.38	$89.40	$89.40
7 purchase totals =	$791.39		$841.6169	$841.62	$841.60	$841.70