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	$190.93	4.507%	$199.5352	$199.54	$199.55	$199.50
Purchase #2	$217.56	5.420%	$229.3518	$229.35	$229.35	$229.40
Purchase #3	$29.70	4.438%	$31.0181	$31.02	$31.00	$31.00
Purchase #4	$143.35	7.540%	$154.1586	$154.16	$154.15	$154.20
Purchase #5	$80.88	10.451%	$89.3328	$89.33	$89.35	$89.30
Purchase #6	$37.26	4.437%	$38.9132	$38.91	$38.90	$38.90
Purchase #7	$172.29	10.688%	$190.7044	$190.70	$190.70	$190.70
7 purchase totals =	$871.97		$933.0141	$933.01	$933.00	$933.00