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	$187.94	6.830%	$200.7763	$200.78	$200.80	$200.80
Purchase #2	$61.84	6.814%	$66.0538	$66.05	$66.05	$66.10
Purchase #3	$154.72	6.553%	$164.8588	$164.86	$164.85	$164.90
Purchase #4	$17.61	8.746%	$19.1502	$19.15	$19.15	$19.20
Purchase #5	$221.45	3.503%	$229.2074	$229.21	$229.20	$229.20
Purchase #6	$196.67	9.291%	$214.9426	$214.94	$214.95	$214.90
Purchase #7	$134.60	3.598%	$139.4429	$139.44	$139.45	$139.40
7 purchase totals =	$974.83		$1,034.4320	$1,034.43	$1,034.45	$1,034.50