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	$82.39	3.854%	$85.5653	$85.57	$85.55	$85.60
Purchase #2	$72.58	10.706%	$80.3504	$80.35	$80.35	$80.40
Purchase #3	$160.77	7.539%	$172.8905	$172.89	$172.90	$172.90
Purchase #4	$247.72	5.471%	$261.2728	$261.27	$261.25	$261.30
Purchase #5	$89.64	7.831%	$96.6597	$96.66	$96.65	$96.70
Purchase #6	$147.89	5.823%	$156.5016	$156.50	$156.50	$156.50
Purchase #7	$101.39	9.233%	$110.7513	$110.75	$110.75	$110.80
7 purchase totals =	$902.38		$963.9916	$963.99	$963.95	$964.20