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	$199.75	9.226%	$218.1789	$218.18	$218.20	$218.20
Purchase #2	$84.46	13.439%	$95.8106	$95.81	$95.80	$95.80
Purchase #3	$79.35	11.582%	$88.5403	$88.54	$88.55	$88.50
Purchase #4	$172.31	13.785%	$196.0629	$196.06	$196.05	$196.10
Purchase #5	$196.90	10.677%	$217.923	$217.92	$217.90	$217.90
Purchase #6	$49.33	4.507%	$51.5533	$51.55	$51.55	$51.60
Purchase #7	$188.73	12.680%	$212.661	$212.66	$212.65	$212.70
7 purchase totals =	$970.83		$1,080.7300	$1,080.72	$1,080.70	$1,080.80