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	$20.98	8.455%	$22.7539	$22.75	$22.75	$22.80
Purchase #2	$208.38	6.577%	$222.0852	$222.09	$222.10	$222.10
Purchase #3	$239.27	6.839%	$255.6337	$255.63	$255.65	$255.60
Purchase #4	$145.69	3.390%	$150.6289	$150.63	$150.65	$150.60
Purchase #5	$88.33	13.740%	$100.4665	$100.47	$100.45	$100.50
Purchase #6	$236.58	4.769%	$247.8625	$247.86	$247.85	$247.90
Purchase #7	$167.65	11.291%	$186.5794	$186.58	$186.60	$186.60
7 purchase totals =	$1,106.88		$1,186.0101	$1,186.01	$1,186.05	$1,186.10