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	$48.92	10.533%	$54.0727	$54.07	$54.05	$54.10
Purchase #2	$34.42	5.658%	$36.3675	$36.37	$36.35	$36.40
Purchase #3	$232.26	10.190%	$255.9273	$255.93	$255.95	$255.90
Purchase #4	$9.51	10.834%	$10.5403	$10.54	$10.55	$10.50
Purchase #5	$64.33	4.383%	$67.1496	$67.15	$67.15	$67.10
Purchase #6	$196.50	9.686%	$215.533	$215.53	$215.55	$215.50
Purchase #7	$73.75	9.853%	$81.0166	$81.02	$81.00	$81.00
7 purchase totals =	$659.69		$720.6070	$720.61	$720.60	$720.50