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	$237.99	11.165%	$264.5616	$264.56	$264.55	$264.60
Purchase #2	$185.68	10.163%	$204.5507	$204.55	$204.55	$204.60
Purchase #3	$98.83	13.419%	$112.092	$112.09	$112.10	$112.10
Purchase #4	$159.71	5.234%	$168.0692	$168.07	$168.05	$168.10
Purchase #5	$138.94	4.378%	$145.0228	$145.02	$145.00	$145.00
Purchase #6	$30.60	10.776%	$33.8975	$33.90	$33.90	$33.90
Purchase #7	$151.45	13.256%	$171.5262	$171.53	$171.55	$171.50
7 purchase totals =	$1,003.20		$1,099.7200	$1,099.72	$1,099.70	$1,099.80