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	$9.67	9.494%	$10.5881	$10.59	$10.60	$10.60
Purchase #2	$155.44	10.726%	$172.1125	$172.11	$172.10	$172.10
Purchase #3	$248.51	13.564%	$282.2179	$282.22	$282.20	$282.20
Purchase #4	$79.31	4.166%	$82.6141	$82.61	$82.60	$82.60
Purchase #5	$99.68	3.150%	$102.8199	$102.82	$102.80	$102.80
Purchase #6	$186.88	5.363%	$196.9024	$196.90	$196.90	$196.90
Purchase #7	$233.38	9.632%	$255.8592	$255.86	$255.85	$255.90
7 purchase totals =	$1,012.87		$1,103.1141	$1,103.11	$1,103.05	$1,103.10