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	$51.97	6.592%	$55.3959	$55.40	$55.40	$55.40
Purchase #2	$153.83	5.864%	$162.8506	$162.85	$162.85	$162.90
Purchase #3	$122.87	4.577%	$128.4938	$128.49	$128.50	$128.50
Purchase #4	$164.48	5.833%	$174.0741	$174.07	$174.05	$174.10
Purchase #5	$240.83	4.607%	$251.925	$251.93	$251.95	$251.90
Purchase #6	$234.50	11.532%	$261.5425	$261.54	$261.55	$261.50
Purchase #7	$11.89	11.632%	$13.273	$13.27	$13.25	$13.30
7 purchase totals =	$980.37		$1,047.5549	$1,047.55	$1,047.55	$1,047.60