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	$200.60	9.104%	$218.8626	$218.86	$218.85	$218.90
Purchase #2	$55.62	6.625%	$59.3048	$59.30	$59.30	$59.30
Purchase #3	$82.29	4.533%	$86.0202	$86.02	$86.00	$86.00
Purchase #4	$246.47	12.223%	$276.596	$276.60	$276.60	$276.60
Purchase #5	$27.33	6.179%	$29.0187	$29.02	$29.00	$29.00
Purchase #6	$227.29	12.197%	$255.0126	$255.01	$255.00	$255.00
Purchase #7	$238.85	8.654%	$259.5201	$259.52	$259.50	$259.50
7 purchase totals =	$1,078.45		$1,184.3350	$1,184.33	$1,184.25	$1,184.30