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	$105.60	6.862%	$112.8463	$112.85	$112.85	$112.80
Purchase #2	$151.49	11.180%	$168.4266	$168.43	$168.45	$168.40
Purchase #3	$186.41	5.212%	$196.1257	$196.13	$196.15	$196.10
Purchase #4	$38.31	10.710%	$42.413	$42.41	$42.40	$42.40
Purchase #5	$110.39	13.665%	$125.4748	$125.47	$125.45	$125.50
Purchase #6	$184.47	9.864%	$202.6661	$202.67	$202.65	$202.70
Purchase #7	$131.57	7.402%	$141.3088	$141.31	$141.30	$141.30
7 purchase totals =	$908.24		$989.2613	$989.27	$989.25	$989.20