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	$113.94	11.576%	$127.1297	$127.13	$127.15	$127.10
Purchase #2	$162.83	5.341%	$171.5268	$171.53	$171.55	$171.50
Purchase #3	$174.49	9.210%	$190.5605	$190.56	$190.55	$190.60
Purchase #4	$245.57	13.731%	$279.2892	$279.29	$279.30	$279.30
Purchase #5	$91.46	12.347%	$102.7526	$102.75	$102.75	$102.80
Purchase #6	$135.58	8.845%	$147.5721	$147.57	$147.55	$147.60
Purchase #7	$71.45	7.850%	$77.0588	$77.06	$77.05	$77.10
7 purchase totals =	$995.32		$1,095.8897	$1,095.89	$1,095.90	$1,096.00