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	$186.77	10.574%	$206.5191	$206.52	$206.50	$206.50
Purchase #2	$168.29	7.789%	$181.3981	$181.40	$181.40	$181.40
Purchase #3	$233.59	11.868%	$261.3125	$261.31	$261.30	$261.30
Purchase #4	$19.42	7.806%	$20.9359	$20.94	$20.95	$20.90
Purchase #5	$233.38	7.742%	$251.4483	$251.45	$251.45	$251.40
Purchase #6	$37.91	6.677%	$40.4413	$40.44	$40.45	$40.40
Purchase #7	$6.31	3.519%	$6.532	$6.53	$6.55	$6.50
7 purchase totals =	$885.67		$968.5872	$968.59	$968.60	$968.40