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	$157.70	5.149%	$165.82	$165.82	$165.80	$165.80
Purchase #2	$14.89	12.669%	$16.7764	$16.78	$16.80	$16.80
Purchase #3	$117.56	11.480%	$131.0559	$131.06	$131.05	$131.10
Purchase #4	$162.83	5.660%	$172.0462	$172.05	$172.05	$172.00
Purchase #5	$245.88	10.477%	$271.6408	$271.64	$271.65	$271.60
Purchase #6	$83.86	4.812%	$87.8953	$87.90	$87.90	$87.90
Purchase #7	$181.84	10.234%	$200.4495	$200.45	$200.45	$200.40
7 purchase totals =	$964.56		$1,045.6841	$1,045.70	$1,045.70	$1,045.60