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	$247.70	11.635%	$276.5199	$276.52	$276.50	$276.50
Purchase #2	$19.80	10.469%	$21.8729	$21.87	$21.85	$21.90
Purchase #3	$236.70	13.476%	$268.5977	$268.60	$268.60	$268.60
Purchase #4	$82.37	12.279%	$92.4842	$92.48	$92.50	$92.50
Purchase #5	$245.81	13.602%	$279.2451	$279.25	$279.25	$279.20
Purchase #6	$6.38	3.835%	$6.6247	$6.62	$6.60	$6.60
Purchase #7	$123.54	13.508%	$140.2278	$140.23	$140.25	$140.20
7 purchase totals =	$962.30		$1,085.5723	$1,085.57	$1,085.55	$1,085.50