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	$44.88	3.857%	$46.611	$46.61	$46.60	$46.60
Purchase #2	$169.54	6.499%	$180.5584	$180.56	$180.55	$180.60
Purchase #3	$171.67	4.627%	$179.6132	$179.61	$179.60	$179.60
Purchase #4	$69.70	10.234%	$76.8331	$76.83	$76.85	$76.80
Purchase #5	$204.52	4.610%	$213.9484	$213.95	$213.95	$213.90
Purchase #6	$129.68	11.531%	$144.6334	$144.63	$144.65	$144.60
Purchase #7	$190.90	4.124%	$198.7727	$198.77	$198.75	$198.80
7 purchase totals =	$980.89		$1,040.9702	$1,040.96	$1,040.95	$1,040.90