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	$81.35	7.681%	$87.5985	$87.60	$87.60	$87.60
Purchase #2	$228.83	4.189%	$238.4157	$238.42	$238.40	$238.40
Purchase #3	$154.69	12.287%	$173.6968	$173.70	$173.70	$173.70
Purchase #4	$203.58	9.202%	$222.3134	$222.31	$222.30	$222.30
Purchase #5	$73.80	13.479%	$83.7475	$83.75	$83.75	$83.70
Purchase #6	$175.41	12.245%	$196.889	$196.89	$196.90	$196.90
Purchase #7	$213.73	8.119%	$231.0827	$231.08	$231.10	$231.10
7 purchase totals =	$1,131.39		$1,233.7436	$1,233.75	$1,233.75	$1,233.70