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	$52.62	3.804%	$54.6217	$54.62	$54.60	$54.60
Purchase #2	$13.96	10.852%	$15.4749	$15.47	$15.45	$15.50
Purchase #3	$82.57	5.326%	$86.9677	$86.97	$86.95	$87.00
Purchase #4	$96.95	8.449%	$105.1413	$105.14	$105.15	$105.10
Purchase #5	$244.96	3.647%	$253.8937	$253.89	$253.90	$253.90
Purchase #6	$186.59	10.644%	$206.4506	$206.45	$206.45	$206.50
Purchase #7	$113.97	12.844%	$128.6083	$128.61	$128.60	$128.60
7 purchase totals =	$791.62		$851.1582	$851.15	$851.10	$851.20