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	$94.89	4.650%	$99.3024	$99.30	$99.30	$99.30
Purchase #2	$51.26	5.740%	$54.2023	$54.20	$54.20	$54.20
Purchase #3	$94.49	6.397%	$100.5345	$100.53	$100.55	$100.50
Purchase #4	$193.70	3.262%	$200.0185	$200.02	$200.00	$200.00
Purchase #5	$54.80	3.761%	$56.861	$56.86	$56.85	$56.90
Purchase #6	$176.81	5.441%	$186.4302	$186.43	$186.45	$186.40
Purchase #7	$50.54	7.705%	$54.4341	$54.43	$54.45	$54.40
7 purchase totals =	$716.49		$751.7830	$751.77	$751.80	$751.70