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	$200.41	7.451%	$215.3425	$215.34	$215.35	$215.30
Purchase #2	$35.42	9.291%	$38.7109	$38.71	$38.70	$38.70
Purchase #3	$153.69	12.183%	$172.4141	$172.41	$172.40	$172.40
Purchase #4	$169.66	11.680%	$189.4763	$189.48	$189.50	$189.50
Purchase #5	$62.91	9.356%	$68.7959	$68.80	$68.80	$68.80
Purchase #6	$53.64	7.766%	$57.8057	$57.81	$57.80	$57.80
Purchase #7	$165.63	12.323%	$186.0406	$186.04	$186.05	$186.00
7 purchase totals =	$841.36		$928.5860	$928.59	$928.60	$928.50