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	$202.70	3.318%	$209.4256	$209.43	$209.45	$209.40
Purchase #2	$102.93	8.282%	$111.4547	$111.45	$111.45	$111.50
Purchase #3	$166.48	4.722%	$174.3412	$174.34	$174.35	$174.30
Purchase #4	$105.63	6.340%	$112.3269	$112.33	$112.35	$112.30
Purchase #5	$166.84	8.641%	$181.2566	$181.26	$181.25	$181.30
Purchase #6	$14.47	7.534%	$15.5602	$15.56	$15.55	$15.60
Purchase #7	$13.70	12.848%	$15.4602	$15.46	$15.45	$15.50
7 purchase totals =	$772.75		$819.8254	$819.83	$819.85	$819.90