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	$201.25	7.126%	$215.5911	$215.59	$215.60	$215.60
Purchase #2	$143.95	4.519%	$150.4551	$150.46	$150.45	$150.50
Purchase #3	$153.90	13.491%	$174.6626	$174.66	$174.65	$174.70
Purchase #4	$24.30	3.861%	$25.2382	$25.24	$25.25	$25.20
Purchase #5	$86.79	3.287%	$89.6428	$89.64	$89.65	$89.60
Purchase #6	$162.72	3.354%	$168.1776	$168.18	$168.20	$168.20
Purchase #7	$185.28	3.527%	$191.8148	$191.81	$191.80	$191.80
7 purchase totals =	$958.19		$1,015.5822	$1,015.58	$1,015.60	$1,015.60