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	$241.49	11.185%	$268.5007	$268.50	$268.50	$268.50
Purchase #2	$139.58	12.614%	$157.1866	$157.19	$157.20	$157.20
Purchase #3	$72.87	10.747%	$80.7013	$80.70	$80.70	$80.70
Purchase #4	$199.94	4.687%	$209.3112	$209.31	$209.30	$209.30
Purchase #5	$54.30	8.828%	$59.0936	$59.09	$59.10	$59.10
Purchase #6	$201.34	10.487%	$222.4545	$222.45	$222.45	$222.50
Purchase #7	$83.63	3.173%	$86.2836	$86.28	$86.30	$86.30
7 purchase totals =	$993.15		$1,083.5315	$1,083.52	$1,083.55	$1,083.60