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	$145.39	3.650%	$150.6967	$150.70	$150.70	$150.70
Purchase #2	$116.68	12.505%	$131.2708	$131.27	$131.25	$131.30
Purchase #3	$51.27	10.118%	$56.4575	$56.46	$56.45	$56.50
Purchase #4	$202.34	6.591%	$215.6762	$215.68	$215.70	$215.70
Purchase #5	$198.78	9.572%	$217.8072	$217.81	$217.80	$217.80
Purchase #6	$76.82	10.805%	$85.1204	$85.12	$85.10	$85.10
Purchase #7	$227.76	11.627%	$254.2417	$254.24	$254.25	$254.20
7 purchase totals =	$1,019.04		$1,111.2705	$1,111.28	$1,111.25	$1,111.30