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	$231.30	6.265%	$245.7909	$245.79	$245.80	$245.80
Purchase #2	$139.78	10.620%	$154.6246	$154.62	$154.60	$154.60
Purchase #3	$122.67	3.567%	$127.0456	$127.05	$127.05	$127.00
Purchase #4	$157.40	10.584%	$174.0592	$174.06	$174.05	$174.10
Purchase #5	$210.34	5.773%	$222.4829	$222.48	$222.50	$222.50
Purchase #6	$207.41	7.190%	$222.3228	$222.32	$222.30	$222.30
Purchase #7	$239.37	3.384%	$247.4703	$247.47	$247.45	$247.50
7 purchase totals =	$1,308.27		$1,393.7963	$1,393.79	$1,393.75	$1,393.80