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	$238.75	3.444%	$246.9726	$246.97	$246.95	$247.00
Purchase #2	$32.88	13.676%	$37.3767	$37.38	$37.40	$37.40
Purchase #3	$47.39	11.539%	$52.8583	$52.86	$52.85	$52.90
Purchase #4	$104.59	10.711%	$115.7926	$115.79	$115.80	$115.80
Purchase #5	$38.90	12.697%	$43.8391	$43.84	$43.85	$43.80
Purchase #6	$209.27	7.657%	$225.2938	$225.29	$225.30	$225.30
Purchase #7	$124.69	13.602%	$141.6503	$141.65	$141.65	$141.70
7 purchase totals =	$796.47		$863.7834	$863.78	$863.80	$863.90