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	$134.86	10.166%	$148.5699	$148.57	$148.55	$148.60
Purchase #2	$124.77	3.273%	$128.8537	$128.85	$128.85	$128.90
Purchase #3	$234.63	12.666%	$264.3482	$264.35	$264.35	$264.30
Purchase #4	$166.38	3.635%	$172.4279	$172.43	$172.45	$172.40
Purchase #5	$182.90	12.208%	$205.2284	$205.23	$205.25	$205.20
Purchase #6	$73.82	6.602%	$78.6936	$78.69	$78.70	$78.70
Purchase #7	$188.35	10.800%	$208.6918	$208.69	$208.70	$208.70
7 purchase totals =	$1,105.71		$1,206.8135	$1,206.81	$1,206.85	$1,206.80