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	$134.42	6.822%	$143.5901	$143.59	$143.60	$143.60
Purchase #2	$168.57	3.349%	$174.2154	$174.22	$174.20	$174.20
Purchase #3	$40.27	5.486%	$42.4792	$42.48	$42.50	$42.50
Purchase #4	$59.49	4.257%	$62.0225	$62.02	$62.00	$62.00
Purchase #5	$146.26	13.782%	$166.4176	$166.42	$166.40	$166.40
Purchase #6	$57.79	9.724%	$63.4095	$63.41	$63.40	$63.40
Purchase #7	$213.75	3.610%	$221.4664	$221.47	$221.45	$221.50
7 purchase totals =	$820.55		$873.6007	$873.61	$873.55	$873.60