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	$215.77	11.344%	$240.2469	$240.25	$240.25	$240.20
Purchase #2	$226.68	13.790%	$257.9392	$257.94	$257.95	$257.90
Purchase #3	$7.86	11.747%	$8.7833	$8.78	$8.80	$8.80
Purchase #4	$139.99	10.545%	$154.7519	$154.75	$154.75	$154.80
Purchase #5	$128.56	6.477%	$136.8868	$136.89	$136.90	$136.90
Purchase #6	$106.72	12.151%	$119.6875	$119.69	$119.70	$119.70
Purchase #7	$78.80	13.579%	$89.5003	$89.50	$89.50	$89.50
7 purchase totals =	$904.38		$1,007.7959	$1,007.80	$1,007.85	$1,007.80