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	$212.92	4.616%	$222.7484	$222.75	$222.75	$222.70
Purchase #2	$83.97	8.142%	$90.8068	$90.81	$90.80	$90.80
Purchase #3	$224.38	12.544%	$252.5262	$252.53	$252.55	$252.50
Purchase #4	$35.57	8.398%	$38.5572	$38.56	$38.55	$38.60
Purchase #5	$178.28	7.838%	$192.2536	$192.25	$192.25	$192.30
Purchase #6	$57.97	12.871%	$65.4313	$65.43	$65.45	$65.40
Purchase #7	$113.27	10.259%	$124.8904	$124.89	$124.90	$124.90
7 purchase totals =	$906.36		$987.2139	$987.22	$987.25	$987.20