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	$157.49	4.669%	$164.8432	$164.84	$164.85	$164.80
Purchase #2	$227.56	13.182%	$257.557	$257.56	$257.55	$257.60
Purchase #3	$53.72	4.748%	$56.2706	$56.27	$56.25	$56.30
Purchase #4	$56.90	3.510%	$58.8972	$58.90	$58.90	$58.90
Purchase #5	$56.87	13.494%	$64.544	$64.54	$64.55	$64.50
Purchase #6	$143.92	8.651%	$156.3705	$156.37	$156.35	$156.40
Purchase #7	$221.47	9.696%	$242.9437	$242.94	$242.95	$242.90
7 purchase totals =	$917.93		$1,001.4262	$1,001.42	$1,001.40	$1,001.40