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	$172.27	9.249%	$188.2033	$188.20	$188.20	$188.20
Purchase #2	$89.91	9.328%	$98.2968	$98.30	$98.30	$98.30
Purchase #3	$183.76	3.327%	$189.8737	$189.87	$189.85	$189.90
Purchase #4	$200.74	11.710%	$224.2467	$224.25	$224.25	$224.20
Purchase #5	$95.52	8.752%	$103.8799	$103.88	$103.90	$103.90
Purchase #6	$168.32	11.814%	$188.2053	$188.21	$188.20	$188.20
Purchase #7	$114.89	7.717%	$123.7561	$123.76	$123.75	$123.80
7 purchase totals =	$1,025.41		$1,116.4618	$1,116.47	$1,116.45	$1,116.50