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	$53.46	13.844%	$60.861	$60.86	$60.85	$60.90
Purchase #2	$72.54	4.469%	$75.7818	$75.78	$75.80	$75.80
Purchase #3	$192.65	13.614%	$218.8774	$218.88	$218.90	$218.90
Purchase #4	$52.97	12.651%	$59.6712	$59.67	$59.65	$59.70
Purchase #5	$183.46	13.693%	$208.5812	$208.58	$208.60	$208.60
Purchase #6	$133.35	6.798%	$142.4151	$142.42	$142.40	$142.40
Purchase #7	$213.80	9.259%	$233.5957	$233.60	$233.60	$233.60
7 purchase totals =	$902.23		$999.7834	$999.79	$999.80	$999.90