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	$79.84	8.709%	$86.7933	$86.79	$86.80	$86.80
Purchase #2	$241.94	11.187%	$269.0058	$269.01	$269.00	$269.00
Purchase #3	$75.59	12.323%	$84.905	$84.91	$84.90	$84.90
Purchase #4	$48.47	10.656%	$53.635	$53.64	$53.65	$53.60
Purchase #5	$114.31	8.388%	$123.8983	$123.90	$123.90	$123.90
Purchase #6	$188.86	8.389%	$204.7035	$204.70	$204.70	$204.70
Purchase #7	$187.64	4.564%	$196.2039	$196.20	$196.20	$196.20
7 purchase totals =	$936.65		$1,019.1448	$1,019.15	$1,019.15	$1,019.10