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	$50.32	7.846%	$54.2681	$54.27	$54.25	$54.30
Purchase #2	$18.72	11.527%	$20.8779	$20.88	$20.90	$20.90
Purchase #3	$219.29	5.585%	$231.5373	$231.54	$231.55	$231.50
Purchase #4	$14.55	10.220%	$16.037	$16.04	$16.05	$16.00
Purchase #5	$62.76	6.714%	$66.9737	$66.97	$66.95	$67.00
Purchase #6	$157.59	10.111%	$173.5239	$173.52	$173.50	$173.50
Purchase #7	$147.62	13.423%	$167.435	$167.44	$167.45	$167.40
7 purchase totals =	$670.85		$730.6529	$730.66	$730.65	$730.60