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	$49.48	10.348%	$54.6002	$54.60	$54.60	$54.60
Purchase #2	$229.90	3.548%	$238.0569	$238.06	$238.05	$238.10
Purchase #3	$124.69	12.576%	$140.371	$140.37	$140.35	$140.40
Purchase #4	$108.41	10.231%	$119.5014	$119.50	$119.50	$119.50
Purchase #5	$36.40	8.570%	$39.5195	$39.52	$39.50	$39.50
Purchase #6	$153.47	5.769%	$162.3237	$162.32	$162.30	$162.30
Purchase #7	$174.82	8.482%	$189.6482	$189.65	$189.65	$189.60
7 purchase totals =	$877.17		$944.0209	$944.02	$943.95	$944.00