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	$179.32	9.602%	$196.5383	$196.54	$196.55	$196.50
Purchase #2	$242.45	5.465%	$255.6999	$255.70	$255.70	$255.70
Purchase #3	$75.62	6.121%	$80.2487	$80.25	$80.25	$80.20
Purchase #4	$169.50	13.157%	$191.8011	$191.80	$191.80	$191.80
Purchase #5	$83.54	12.471%	$93.9583	$93.96	$93.95	$94.00
Purchase #6	$100.83	13.647%	$114.5903	$114.59	$114.60	$114.60
Purchase #7	$158.64	8.682%	$172.4131	$172.41	$172.40	$172.40
7 purchase totals =	$1,009.90		$1,105.2497	$1,105.25	$1,105.25	$1,105.20