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	$213.47	4.367%	$222.7922	$222.79	$222.80	$222.80
Purchase #2	$250.45	4.183%	$260.9263	$260.93	$260.95	$260.90
Purchase #3	$176.98	4.779%	$185.4379	$185.44	$185.45	$185.40
Purchase #4	$163.48	11.215%	$181.8143	$181.81	$181.80	$181.80
Purchase #5	$175.25	11.865%	$196.0434	$196.04	$196.05	$196.00
Purchase #6	$129.93	8.770%	$141.3249	$141.32	$141.30	$141.30
Purchase #7	$62.29	7.520%	$66.9742	$66.97	$66.95	$67.00
7 purchase totals =	$1,171.85		$1,255.3132	$1,255.30	$1,255.30	$1,255.20