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	$180.69	13.463%	$205.0163	$205.02	$205.00	$205.00
Purchase #2	$61.59	4.579%	$64.4102	$64.41	$64.40	$64.40
Purchase #3	$174.61	5.104%	$183.5221	$183.52	$183.50	$183.50
Purchase #4	$6.79	13.320%	$7.6944	$7.69	$7.70	$7.70
Purchase #5	$160.95	13.659%	$182.9342	$182.93	$182.95	$182.90
Purchase #6	$160.77	5.128%	$169.0143	$169.01	$169.00	$169.00
Purchase #7	$177.60	10.649%	$196.5126	$196.51	$196.50	$196.50
7 purchase totals =	$923.00		$1,009.1041	$1,009.09	$1,009.05	$1,009.00