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	$117.73	11.783%	$131.6021	$131.60	$131.60	$131.60
Purchase #2	$219.81	4.483%	$229.6641	$229.66	$229.65	$229.70
Purchase #3	$61.26	11.476%	$68.2902	$68.29	$68.30	$68.30
Purchase #4	$174.52	12.575%	$196.4659	$196.47	$196.45	$196.50
Purchase #5	$72.58	13.264%	$82.207	$82.21	$82.20	$82.20
Purchase #6	$34.81	3.672%	$36.0882	$36.09	$36.10	$36.10
Purchase #7	$12.69	7.675%	$13.664	$13.66	$13.65	$13.70
7 purchase totals =	$693.40		$757.9815	$757.98	$757.95	$758.10