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	$229.55	8.669%	$249.4497	$249.45	$249.45	$249.40
Purchase #2	$168.95	4.276%	$176.1743	$176.17	$176.15	$176.20
Purchase #3	$82.99	9.811%	$91.1321	$91.13	$91.15	$91.10
Purchase #4	$66.95	7.357%	$71.8755	$71.88	$71.90	$71.90
Purchase #5	$247.55	4.563%	$258.8457	$258.85	$258.85	$258.80
Purchase #6	$73.89	6.531%	$78.7158	$78.72	$78.70	$78.70
Purchase #7	$35.57	6.440%	$37.8607	$37.86	$37.85	$37.90
7 purchase totals =	$905.45		$964.0538	$964.06	$964.05	$964.00