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	$71.48	10.283%	$78.8303	$78.83	$78.85	$78.80
Purchase #2	$228.51	10.644%	$252.8326	$252.83	$252.85	$252.80
Purchase #3	$177.76	9.806%	$195.1911	$195.19	$195.20	$195.20
Purchase #4	$86.26	13.781%	$98.1475	$98.15	$98.15	$98.10
Purchase #5	$219.41	9.655%	$240.594	$240.59	$240.60	$240.60
Purchase #6	$176.87	11.112%	$196.5238	$196.52	$196.50	$196.50
Purchase #7	$168.80	8.161%	$182.5758	$182.58	$182.60	$182.60
7 purchase totals =	$1,129.09		$1,244.6951	$1,244.69	$1,244.75	$1,244.60