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	$182.54	7.762%	$196.7088	$196.71	$196.70	$196.70
Purchase #2	$156.44	7.746%	$168.5578	$168.56	$168.55	$168.60
Purchase #3	$34.92	5.619%	$36.8822	$36.88	$36.90	$36.90
Purchase #4	$49.98	11.322%	$55.6387	$55.64	$55.65	$55.60
Purchase #5	$40.86	8.377%	$44.2828	$44.28	$44.30	$44.30
Purchase #6	$138.94	5.757%	$146.9388	$146.94	$146.95	$146.90
Purchase #7	$133.42	5.490%	$140.7448	$140.74	$140.75	$140.70
7 purchase totals =	$737.10		$789.7539	$789.75	$789.80	$789.70