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	$96.65	7.368%	$103.7712	$103.77	$103.75	$103.80
Purchase #2	$35.32	12.227%	$39.6386	$39.64	$39.65	$39.60
Purchase #3	$47.75	3.833%	$49.5803	$49.58	$49.60	$49.60
Purchase #4	$69.55	3.122%	$71.7214	$71.72	$71.70	$71.70
Purchase #5	$136.94	11.421%	$152.5799	$152.58	$152.60	$152.60
Purchase #6	$30.45	6.234%	$32.3483	$32.35	$32.35	$32.30
Purchase #7	$51.72	10.118%	$56.953	$56.95	$56.95	$57.00
7 purchase totals =	$468.38		$506.5927	$506.59	$506.60	$506.60