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	$189.85	3.319%	$196.1511	$196.15	$196.15	$196.20
Purchase #2	$199.33	12.685%	$224.615	$224.62	$224.60	$224.60
Purchase #3	$112.92	10.303%	$124.5541	$124.55	$124.55	$124.60
Purchase #4	$148.54	3.832%	$154.2321	$154.23	$154.25	$154.20
Purchase #5	$62.51	4.559%	$65.3598	$65.36	$65.35	$65.40
Purchase #6	$39.36	7.651%	$42.3714	$42.37	$42.35	$42.40
Purchase #7	$65.32	11.636%	$72.9206	$72.92	$72.90	$72.90
7 purchase totals =	$817.83		$880.2041	$880.20	$880.15	$880.30