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	$182.67	3.629%	$189.2991	$189.30	$189.30	$189.30
Purchase #2	$94.29	9.786%	$103.5172	$103.52	$103.50	$103.50
Purchase #3	$7.29	5.823%	$7.7145	$7.71	$7.70	$7.70
Purchase #4	$92.66	13.398%	$105.0746	$105.07	$105.05	$105.10
Purchase #5	$236.54	3.377%	$244.528	$244.53	$244.55	$244.50
Purchase #6	$182.68	11.465%	$203.6243	$203.62	$203.60	$203.60
Purchase #7	$80.77	12.453%	$90.8283	$90.83	$90.85	$90.80
7 purchase totals =	$876.90		$944.5860	$944.58	$944.55	$944.50