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	$59.44	5.641%	$62.793	$62.79	$62.80	$62.80
Purchase #2	$199.51	11.744%	$222.9405	$222.94	$222.95	$222.90
Purchase #3	$114.67	13.822%	$130.5197	$130.52	$130.50	$130.50
Purchase #4	$197.62	3.865%	$205.258	$205.26	$205.25	$205.30
Purchase #5	$27.69	4.275%	$28.8737	$28.87	$28.85	$28.90
Purchase #6	$25.95	7.504%	$27.8973	$27.90	$27.90	$27.90
Purchase #7	$19.94	13.313%	$22.5946	$22.59	$22.60	$22.60
7 purchase totals =	$644.82		$700.8768	$700.87	$700.85	$700.90