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	$224.78	12.227%	$252.2639	$252.26	$252.25	$252.30
Purchase #2	$81.62	5.233%	$85.8912	$85.89	$85.90	$85.90
Purchase #3	$79.48	12.549%	$89.4539	$89.45	$89.45	$89.50
Purchase #4	$35.66	12.835%	$40.237	$40.24	$40.25	$40.20
Purchase #5	$178.81	11.378%	$199.155	$199.16	$199.15	$199.20
Purchase #6	$111.42	11.114%	$123.8032	$123.80	$123.80	$123.80
Purchase #7	$102.55	12.224%	$115.0857	$115.09	$115.10	$115.10
7 purchase totals =	$814.32		$905.8899	$905.89	$905.90	$906.00