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	$212.28	11.378%	$236.4332	$236.43	$236.45	$236.40
Purchase #2	$233.50	11.307%	$259.9018	$259.90	$259.90	$259.90
Purchase #3	$183.75	6.809%	$196.2615	$196.26	$196.25	$196.30
Purchase #4	$20.42	7.380%	$21.927	$21.93	$21.95	$21.90
Purchase #5	$88.97	7.841%	$95.9461	$95.95	$95.95	$95.90
Purchase #6	$104.48	11.296%	$116.2821	$116.28	$116.30	$116.30
Purchase #7	$67.76	13.828%	$77.1299	$77.13	$77.15	$77.10
7 purchase totals =	$911.16		$1,003.8816	$1,003.88	$1,003.95	$1,003.80