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	$241.83	5.659%	$255.5152	$255.52	$255.50	$255.50
Purchase #2	$121.89	6.317%	$129.5898	$129.59	$129.60	$129.60
Purchase #3	$80.58	7.217%	$86.3955	$86.40	$86.40	$86.40
Purchase #4	$195.93	5.277%	$206.2692	$206.27	$206.25	$206.30
Purchase #5	$9.62	4.597%	$10.0622	$10.06	$10.05	$10.10
Purchase #6	$175.32	4.677%	$183.5197	$183.52	$183.50	$183.50
Purchase #7	$119.98	9.517%	$131.3985	$131.40	$131.40	$131.40
7 purchase totals =	$945.15		$1,002.7501	$1,002.76	$1,002.70	$1,002.80