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	$201.77	10.379%	$222.7117	$222.71	$222.70	$222.70
Purchase #2	$167.28	11.462%	$186.4536	$186.45	$186.45	$186.50
Purchase #3	$126.91	10.217%	$139.8764	$139.88	$139.90	$139.90
Purchase #4	$52.38	6.359%	$55.7108	$55.71	$55.70	$55.70
Purchase #5	$68.75	11.703%	$76.7958	$76.80	$76.80	$76.80
Purchase #6	$112.89	13.409%	$128.0274	$128.03	$128.05	$128.00
Purchase #7	$212.56	9.659%	$233.0912	$233.09	$233.10	$233.10
7 purchase totals =	$942.54		$1,042.6669	$1,042.67	$1,042.70	$1,042.70