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	$247.66	11.478%	$276.0864	$276.09	$276.10	$276.10
Purchase #2	$85.83	7.460%	$92.2329	$92.23	$92.25	$92.20
Purchase #3	$137.37	9.202%	$150.0108	$150.01	$150.00	$150.00
Purchase #4	$82.47	9.127%	$89.997	$90.00	$90.00	$90.00
Purchase #5	$55.94	6.537%	$59.5968	$59.60	$59.60	$59.60
Purchase #6	$17.46	8.342%	$18.9165	$18.92	$18.90	$18.90
Purchase #7	$64.61	7.792%	$69.6444	$69.64	$69.65	$69.60
7 purchase totals =	$691.34		$756.4848	$756.49	$756.50	$756.40