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	$63.42	5.746%	$67.0641	$67.06	$67.05	$67.10
Purchase #2	$56.34	5.180%	$59.2584	$59.26	$59.25	$59.30
Purchase #3	$77.45	12.377%	$87.036	$87.04	$87.05	$87.00
Purchase #4	$187.89	4.777%	$196.8655	$196.87	$196.85	$196.90
Purchase #5	$71.84	12.183%	$80.5923	$80.59	$80.60	$80.60
Purchase #6	$229.59	4.555%	$240.0478	$240.05	$240.05	$240.00
Purchase #7	$231.58	6.658%	$246.9986	$247.00	$247.00	$247.00
7 purchase totals =	$918.11		$977.8627	$977.87	$977.85	$977.90