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	$40.86	9.681%	$44.8157	$44.82	$44.80	$44.80
Purchase #2	$20.50	4.676%	$21.4586	$21.46	$21.45	$21.50
Purchase #3	$67.43	12.721%	$76.0078	$76.01	$76.00	$76.00
Purchase #4	$79.87	11.210%	$88.8234	$88.82	$88.80	$88.80
Purchase #5	$118.25	4.534%	$123.6115	$123.61	$123.60	$123.60
Purchase #6	$210.64	5.822%	$222.9035	$222.90	$222.90	$222.90
Purchase #7	$241.57	6.532%	$257.3494	$257.35	$257.35	$257.30
7 purchase totals =	$779.12		$834.9699	$834.97	$834.90	$834.90