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	$146.64	9.391%	$160.411	$160.41	$160.40	$160.40
Purchase #2	$138.84	7.222%	$148.867	$148.87	$148.85	$148.90
Purchase #3	$41.90	13.354%	$47.4953	$47.50	$47.50	$47.50
Purchase #4	$128.88	10.586%	$142.5232	$142.52	$142.50	$142.50
Purchase #5	$161.41	13.281%	$182.8469	$182.85	$182.85	$182.80
Purchase #6	$186.52	4.422%	$194.7679	$194.77	$194.75	$194.80
Purchase #7	$96.65	8.687%	$105.046	$105.05	$105.05	$105.00
7 purchase totals =	$900.84		$981.9573	$981.97	$981.90	$981.90