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	$145.59	13.696%	$165.53	$165.53	$165.55	$165.50
Purchase #2	$59.78	6.541%	$63.6902	$63.69	$63.70	$63.70
Purchase #3	$133.32	8.287%	$144.3682	$144.37	$144.35	$144.40
Purchase #4	$218.42	7.619%	$235.0614	$235.06	$235.05	$235.10
Purchase #5	$212.46	9.785%	$233.2492	$233.25	$233.25	$233.20
Purchase #6	$151.46	10.589%	$167.4981	$167.50	$167.50	$167.50
Purchase #7	$131.88	12.603%	$148.5008	$148.50	$148.50	$148.50
7 purchase totals =	$1,052.91		$1,157.8979	$1,157.90	$1,157.90	$1,157.90