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	$49.42	10.198%	$54.4599	$54.46	$54.45	$54.50
Purchase #2	$151.94	10.752%	$168.2766	$168.28	$168.30	$168.30
Purchase #3	$235.66	9.526%	$258.109	$258.11	$258.10	$258.10
Purchase #4	$248.46	3.256%	$256.5499	$256.55	$256.55	$256.50
Purchase #5	$25.69	4.725%	$26.9039	$26.90	$26.90	$26.90
Purchase #6	$153.32	12.614%	$172.6598	$172.66	$172.65	$172.70
Purchase #7	$200.63	4.643%	$209.9453	$209.95	$209.95	$209.90
7 purchase totals =	$1,065.12		$1,146.9044	$1,146.91	$1,146.90	$1,146.90