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	$50.37	11.314%	$56.0689	$56.07	$56.05	$56.10
Purchase #2	$233.28	9.547%	$255.5512	$255.55	$255.55	$255.60
Purchase #3	$240.96	12.339%	$270.6921	$270.69	$270.70	$270.70
Purchase #4	$54.37	9.158%	$59.3492	$59.35	$59.35	$59.30
Purchase #5	$184.64	13.761%	$210.0483	$210.05	$210.05	$210.00
Purchase #6	$198.81	4.869%	$208.4901	$208.49	$208.50	$208.50
Purchase #7	$208.84	8.143%	$225.8458	$225.85	$225.85	$225.80
7 purchase totals =	$1,171.27		$1,286.0456	$1,286.05	$1,286.05	$1,286.00