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	$178.75	11.271%	$198.8969	$198.90	$198.90	$198.90
Purchase #2	$68.92	6.347%	$73.2944	$73.29	$73.30	$73.30
Purchase #3	$168.93	7.678%	$181.9004	$181.90	$181.90	$181.90
Purchase #4	$95.65	4.577%	$100.0279	$100.03	$100.05	$100.00
Purchase #5	$168.31	8.253%	$182.2006	$182.20	$182.20	$182.20
Purchase #6	$243.25	13.257%	$275.4977	$275.50	$275.50	$275.50
Purchase #7	$73.91	5.788%	$78.1879	$78.19	$78.20	$78.20
7 purchase totals =	$997.72		$1,090.0058	$1,090.01	$1,090.05	$1,090.00