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	$63.85	10.701%	$70.6826	$70.68	$70.70	$70.70
Purchase #2	$214.71	10.564%	$237.392	$237.39	$237.40	$237.40
Purchase #3	$117.59	4.223%	$122.5558	$122.56	$122.55	$122.60
Purchase #4	$78.96	8.836%	$85.9369	$85.94	$85.95	$85.90
Purchase #5	$211.83	8.525%	$229.8885	$229.89	$229.90	$229.90
Purchase #6	$193.52	9.795%	$212.4753	$212.48	$212.50	$212.50
Purchase #7	$159.55	8.340%	$172.8565	$172.86	$172.85	$172.90
7 purchase totals =	$1,040.01		$1,131.7876	$1,131.80	$1,131.85	$1,131.90