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	$203.60	9.206%	$222.3434	$222.34	$222.35	$222.30
Purchase #2	$119.28	3.797%	$123.8091	$123.81	$123.80	$123.80
Purchase #3	$52.61	11.131%	$58.466	$58.47	$58.45	$58.50
Purchase #4	$155.76	8.382%	$168.8158	$168.82	$168.80	$168.80
Purchase #5	$18.89	6.374%	$20.094	$20.09	$20.10	$20.10
Purchase #6	$188.68	12.399%	$212.0744	$212.07	$212.05	$212.10
Purchase #7	$193.34	11.283%	$215.1546	$215.15	$215.15	$215.20
7 purchase totals =	$932.16		$1,020.7573	$1,020.75	$1,020.70	$1,020.80