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	$30.38	6.391%	$32.3216	$32.32	$32.30	$32.30
Purchase #2	$192.49	10.364%	$212.4397	$212.44	$212.45	$212.40
Purchase #3	$7.37	7.782%	$7.9435	$7.94	$7.95	$7.90
Purchase #4	$33.69	13.134%	$38.1148	$38.11	$38.10	$38.10
Purchase #5	$169.28	12.563%	$190.5466	$190.55	$190.55	$190.50
Purchase #6	$57.83	4.595%	$60.4873	$60.49	$60.50	$60.50
Purchase #7	$107.52	3.374%	$111.1477	$111.15	$111.15	$111.10
7 purchase totals =	$598.56		$653.0012	$653.00	$653.00	$652.80