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	$133.88	5.595%	$141.3706	$141.37	$141.35	$141.40
Purchase #2	$155.85	5.815%	$164.9127	$164.91	$164.90	$164.90
Purchase #3	$241.67	10.486%	$267.0115	$267.01	$267.00	$267.00
Purchase #4	$33.64	8.182%	$36.3924	$36.39	$36.40	$36.40
Purchase #5	$98.70	10.790%	$109.3497	$109.35	$109.35	$109.30
Purchase #6	$169.28	5.810%	$179.1152	$179.12	$179.10	$179.10
Purchase #7	$42.27	13.265%	$47.8771	$47.88	$47.90	$47.90
7 purchase totals =	$875.29		$946.0292	$946.03	$946.00	$946.00